I do 1 of 2 things. I either place them on a shelf behind me after cutting a project up. After the project is completed I will sort sizes. Small sizes are given to my quilt guild on the 'Free Table". Larger sizes are folded neatly and put on a shelving unit that is categorized as 'lights- mediums- darks. This works best for me.
2nd is to take out my Studio cutter and cut apple cores. The last ones I made were to cut 5" squares for a Pat Speth quilt. It just depends on colors and a project I want to make next. The only sizes I really keep that are small are strings. I want to make a string quilt again. I loved my last one which was a Bonnie Hunter design from String Fling.