I wanted to make sure the mycelium was fully dry before photographing it, so I let the pieces dry for a number of weeks as opposed to just the couple days recommended before baking. Now I have two bases with three slices each, and an additional bottom slice that may be attached to one of the larger sections.
Today I tried to remove the weights (books) from the mycelium and pull the plastic away from the sides so the white coating can start to grow. I had some metal toilet paper holders, so I clipped the plastic bag to the holders to pull it away from the mycelium. There will probably still be some places where the plastic touches, but it should allow much more of the coating to develop than my last attempt. In the process, I accidentally pulled one of the layers off of the base, so I added the books back. Hopefully it will stitch together again (and be stronger than it was before).
Today I demolded the mycelium slices and stacked them. The cups do seem to have taken up more space in the mold than the last spacers I used, which explains the extra mycelium I had. Since my oven can only fit 3 slices stacked at once, I chose not to add the fourth slice at this stage. I might add it after they are fully dry, or maybe not at all.
While stacking the slices, I tried to press them together a little bit to help fill in some of the gaps that were left in my first attempt, so we will have to see how that works.
In a few days I will try to pull the plastic away so the mycelium can grow the white coating over it, then I will leave everything out to dry.