I have a box full of different empty containers with their lids. Each container is a different size or different color. Some have screw-on lids and some lids pop on and off. I set them all out in front of J and had him match the lids to the containers. We talked about the shape of the container and looked for a similary shaped lid and then he practiced placing the lid on the container himself. He still has trouble with screw-on lids (he keeps wanting to screw them back and forth and of course they’ll never get tight that way!). You might have seen this post that describes one of J’s chores (that he thinks is a game!). Whether as a chore or just for fun, this activity is an easy way to keep him busy for awhile 
and it’s good practice for him too!
Age attempted: 23 months, could be done much earlier though they might need more help with screw-on lids
Teachable moments: size, shape, practice with motor skills when attaching lids
I am delighted that I just randomly came across your website! You have wonderful ideas and simple projects… love it! I, too am a stay-at-home mom and my son is just entering pre-toddler-hood.
Thank you for sharing your ideas!