obeydesign

You'll need to place the six fields (Field 1, Field 2, ... Field 6) in six separate Text or Picture frames on your poster. Group them (the group will be one of your populated frames) and duplicate that group, move it, repeat 2998 times filling the poster. Generate it. You should have one page with the 3000 records x 6 fields.
Try it with 10 to 20 records first.

If the 3000 should result in 1 page (poster) then you would use the Data Merge Layout tool – which you excluded in your initial post, which seems you want 1 record per page and a result of 3000 pages (which makes your info "poster-sized" irrelevant). So I still don't understand what exactly you are asking for.
If your topic concerns the amount of 3000 I can't answer but you could do a quick test with any source of 3000 records in any rough layout. If the number of possible records or pages is limited to less than 3000, a workaround could be to generate the desired result in several steps (e.g. run Data Margin 2x with a split source) and then combine the results (e.g. via the menu Document > Add Pages from File).
Since I am able to create an .afpub with 3000 pages, and also a data merge setup with 3000 records, I doubt that 3000 is a limit in APub "by design".
  
So the success of the procedure may depend on the hardware, processing time or APub's ability to handle the content for this number of layouts without freezing or crashing. I mention the latter because right now I experienced APub freezing (without increasing CPU/GPU use in the macOS Activity Monitor app) when I wanted to switch a facing page document of 3000 entirely empty pages to a document of single pages (I had expected to be done in a second but still wasn't finished after about a minute, so I quit APub).

What does one record look like? Is it one field with a word in it or several fields with words and pictures?

I am not sure what you mean by flexible respectively by fluid. I would understand both adjectives here as irregularly repetitive, perhaps with different sizes and angles among the 3000 records. This would not fit the data merging feature in APub, which works rather with a strictly rectangular grid like a simple table, ideal for exact repetition of 1 layout for each record (maybe that is why you ask for a way without using the data merge tool?).
That means to achieve a flexible layout or fluid, possibly organic or coincidentally appearance it would require many separate manually created fields ... while with increased flexibility the advantage of the auto-generated data merge layout would get reduced.

Hi @obeydesign,
You don't have to use the Data Merge Layout tool, you can just insert the Field into a text box or picture frame on the page and then complete your merge.
 

Wouldn't it be more appropriate to ask that in a Silhouette forum, rather than an Affinity forum?

I seem to have gotten it to work. Thank you everyone.

@obeydesign, in case it still is not clear to you, note that in Affinity the capital L type of Layer (like is shown in parentheses in the Layers panel) is a particular kind of container layer, similar to but not the same as a group layer (like those shown in the Layers panel with the word "Group" enclosed in parentheses).

Just start with two rectangle layers and nothing more here first! - Aka ...

layer_test.afdesign layer_test.pdf  
 
 

I believe what you have are Named Groups, not Layers.
I've attached a PDF--try it, please. There should be 3 layers in Silhouette Studio, plus a grouped object not on a layer.
I've also attached the AD file so you can review.
untitled.afdesign Untitled.pdf

Each Square is a layer on it's own here! - Aka every (Curve) is already a layer and every (Rectangle) too!

 

They should be labeled (Layer) in the Layers panel, which is what you get from the menu Layer > New Layer that I suggested earlier. You have several of those; I think you may need more.

The question is if the Silhouette software can deal with groups of layers and groups at all? - Further I would start with a simpler just a few layers only AD example, exporting that as PDF and then trying to import that correctly usable into the Silhouette software. If that works then enhancing the AD example accordingly, so all in all trying out small steps first before going over to make bigger steps here.

Thanks for the screenshots.
I'm not sure what your Silhouette software requires, so I can't say much more. But it looks like you still have 4 groupings (e.g., Art, Bleeds, and one or two others) that are not in Layer layers.

See further:
How to Use PDF Files in Silhouette Studio (Youtube video)
Import SVG and PDF files (Designer Edition Feature) - video
https://www.cinoradesign.ch/welches-ist-das-richtige-dateiformat-zum-plotten/

You can tell Designer to include Layers in the PDF, by clicking on the More button in the PDF Export dialog and choosing the option. But you will also need to use the menu option Layer > New Layer (or the icon at the bottom of the Layers panel) to create these special container layers, which will show up as (Layer) in the Layers panel. And you will need to organize your objects into the Layers you need them to be in.
Then, if you are lucky, your other application will handle them as you want it to.

Hi @obeydesign,
Unfortunately Affinity doesn't have a direct equivalent of this panel, nor does it support scripting currently, my apologies.
I believe that the Resource Manager is currently the best option that we have implemented, therefore I'll move this thread to the feedback section of our forums for our devs to see and consider adding this in a future update

You are no ordinary mortal. Thank you again!