My first advice is to measure a stack of 20 chips of each color to make sure they are all the same.
Many custom clay chips have a difference between colors.
On www.Chiptalk.net there are many threads discussing trays, such as which tray will fit 20 chips measuring 69mm, 69.5mm, or 70mm etc.
When I got my custom clay chips some colors were too snug (just barely) to fit 20 to a row.
After some use they came to fit ok on their own.