How I organize my blocks using just 3 pins.
For pins, I have some that have an arrow on the top to indicate which part is "UP" on a block. They really help me keep from turning the blocks the wrong way when piecing. The other pins I use on my design wall are the flathead flower pins in yellow. Then I take a marker and write numbers on them. These I use to indicate positions of rows and blocks. I also take some of these and write letters on them, so I can mark a block with just three pins. One for it's row number and one for it's position in the row. If the top of the block isn't easy to tell, I add a 3rd pin with the arrow pointing up to the top of the block.
A block would be marked with, for example, a pin that has "A" on it to show it's row, and a pin with 1, to show it's the first block in the first row. And of course, the "UP" arrow pin when a block needs to be placed in one direction. Some blocks are the same on all sides, in which case you do not need an arrow pin.
I keep the pins stuck in the flannel of my design wall so they are handy when I need them.
You'd think I would never make position mistakes with this system, but when the fibro fog comes in, I will still get things confused. LOL