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.
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.