I forgot to explain that I'm using the bitmap fill to create the pattern.
This is what I did:

1- imported the base tile
2- created a 20"x20" square (without outlines)
3- select the square and applied the bitmap fill as a "repeating tile" and used CTRL + image handles to resize the tiles while keeping the same width and length ratio.



I didn't use the method of snapping many base tiles to create a larger square.