What do These 4 Blocks

Have In Common?

These 4 blocks, although different from each other, have a similar structure. If you can identify that structure, you can use it to design blocks of your own.

They all have a small square in the center and 4 large patterned squares in the corners.

The corner squares are designed on a 3x3 grid and are all the same.

You can design blocks like these by first creating a pattern on a 3x3 grid and then inserting it into the corners of the block.  Let me try a couple.

These are just quick thoughts off the top of my head. I'm sure you could do more, and better.