Here's what I ended up doing: I put 15 (I think) block pieces on paper plates, then the last several I laid out on squares of freezer paper, which I piled up for lack of space. When I got down to the last 2 blocks, I couldn't finish because of unwanted repeats. So I pulled out a paper plate (from the bottom of the stack for no apparent reason), laid the block out, and managed to switch out all the pieces I needed!