There's actually another thread on here that provides the equation to find the weight of oils you'll need for a particular mold. The equation is volume of mold x .40. There was a lot of speculation about where the .40 came from as it didn't work out exactly for some people, myself included. My hypothesis is that the .40 is a standard number representing the water % in the given recipe. I've adjusted that number several times in a couple different molds to the actual water % in my given recipe and it worked out almost perfect every time. More testing is needed to actually prove this theory but so far it has worked out perfect for me. So for those who haven't seen that thread, the equation I'm using is this:
Length x Width x Depth= Volume of mold
Volume of mold x water % in recipe(.40 for 40% water, .38 for 38% water, etc). Hopefully this helps somebody else and I'm not the only one it works for, lol!
As for the parchment/freezer paper debate hopefully it is a thing if the past for me. I'm building a wooden soap mold with a lexan liner so if all goes as well as it did in my head I'll never need to measure and cut another sheet of parchment paper unless I'm trying to line a sheet pan for baking, lol! I'm finding, however, that cutting perfect edges on a sheet of lexan can be challenging at best. I'm used to wood. Plastics are a bit above my pay grade, lol!