One of my littlest’s favorite gifts was a packet of stiff 8×12 colorful felt pieces (today’s edition of #unexpectedtoys). He loves to use them as part of his small world and block play, creating different landscapes for his characters to play on. Blue might be a swimming pool or an ocean when placed next to yellow sand. Green works well for grass and a place for the Paw Patrol to use the potty. ;) Brown is dirt, and when he laid down all the colors it became a trampoline park.
To store when not being played with, I used a file organizer I had on hand and arranged them by color/shade to make it easy to find exactly the piece that’s needed.