I also like the "clam shell" plastic boxes veggies and fruits come in from Sam's Club. (They are a bit larger than the grocery store sized boxes.) I use grape tomato boxes for 5" squares and strawberry boxes for jelly roll sized strips, rolled up. The long, flatter boxes, like cherries come in, I use for smaller 4 in. crumb blocks I am collecting as I sew other things and use the "crumbs" as my starters and enders when piecing. They all stack together nicely, I can see through them, and they don't cost me a penny!