MonTiki

I did select/check the transparent background. What would be the best way to share the file?

Hi I'm new to Affinity Designer and so far love it. I'm reaching out for help / tutorial. I am working on a t-shirt design that is layers over an oval shape. When I send off my design to the printer it shows the oval shape on a white box. Is there a way to just save the shape without the background? I have included an image of what is happening. Thank you