I saw a Pinterest where they used a clear plastic shoe back-of-door hanger and sorted by color for easy to see organization.
I don't cute down into 2.5 sq.---I keep sizes less that FQ and about 6" sq in a plastic drawer stack and stuff all strings into bags as I do more string quilts. I keep a white/lights, a black/gray/dark brown bag and the rest altogether. Wish I could figure a better way to sort is this is almost any size string.