I do miss my brain…OMG, it is awful. Constant state of brain fog over here. Getting older is kind of a crazy process, even if you're expecting the changes.
Instead of black, what do you think about the brownish soap in the OP? It shows the bevels really well. You could also do thin bars, I’m thinking 1”x3”x1” which would still give you an idea but less wastage.
I really like the idea of drawing the designs on graph paper. I have just been using one rounded key and really should use more for variety.