It's a little numbered parking lot, made out of a box lid. First I cut a little driveway in the end. Then simply draw lines for parking spots and number them with a Sharpie, and number the cars. I put the numbers on painters' tape and stuck them to the cars for easy removal. Then drive and park and practice numbers!
Colter was pretty pleased with it, and I found him going back to it himself throughout the day, so that's a real win.