I build Tessellations using Affinity Design in normal mode (not Isometric).
To do this, I create Shapes, adjust their size + arrange them to build a Pattern:
So that the Shapes snap within a Pattern and so that the
Pattern when duplicated, snaps within a Tessellation (as demonstrated in the 3 images below)
Below I describe my workflow followed by questions looking to make my process more efficient.
WORKFLOW
Step #1 - Find Shape Dimensions for Pattern