Trimming creates quite a bit of clay for recycling. The clay is allowed to dry then added to a bucket of water which is instantly absorbed, breaking it down into particles. The slurry, potter talk for mud, is placed on thick plaster slabs where the excess water is absorbed. Now back to being clay, it'll be wedged or de-aired and used again.
While I'm now comfortable making the platters, I'm still trying to get a feel for trimming. I've trimmed the bottoms out of a few platters, and some I cut off at an awkward angle, making them difficult to trim. I'm sharing my failures with you because it's a part of learning; it's the part that makes succeeding fun.