I use the same soft drink flats (with approximately 1 1/2" sides) in class
when we are doing subtractive plaster projects. The large majority of the mess
falls into the box, which is emptied at the end of the period. We also pull
them out on projects with lots of pieces, so each student can keep theirs
together from day to day.
I go to a couple of convenience stores and have them save the flats for me a
week or two before I need new ones. They are very obliging. I explain that
they must be from soft drinks, that use of alcohol products' logos is not
appropriate in an educational environment.
On a sort of similar note, I got an idea from a teacher in a neighboring
county -- I cut up old masonite in 6" squares for each student to put their
ceramic pieces on as they work on them. It makes transporting them from shelf
to table and back easy and seems to keep each individual's work safer because
they have their "own space." I have larger ones for students doing more
horizontal pieces, but most are happy to confine their bases to the smaller