Here are my non-entry photos, and my observations :
1. As someone who can't cut straight bevels even with a wire cutter and a planner/beveler, this technique was very challenging for me. Without really straight and plumb sides, I couldn't get a snug fit to the pieces. The small size of my pieces didn't help; a design with larger pieces would probably have been much easier, since it would have allowed more surface area for better contact/gripping.
2. I had to use a LOT more water than what Grace used in the videos. My soap needed a very softened layer on the top before it would even sort of stick together. My recipe is mostly hard oils, and I'm guessing that had something to do with why it didn't stick as easily without gobs of water to soften up the fresh soap.
3. I crammed my bars into the bottom of my small loaf mold. This was a nice way to hold them together in the oven.
4. My soap didn't soften in the oven. I ended up doing 40 minutes on 200, and it was barely soft to the touch. My oven is spot-on for temperature, so my guess again is the hard oils were the culprit. If I were planning a new batch just for this challenge, I'd do a recipe with more soft oils, and leave out the SL, or any hardening ingredient that you might use in your regular recipe, such as beeswax.
5. My attempts at post-cook planing caused the rim to break in places, and further exposed the seam gaps. It also smeared some of the soap across the front, but I was hesitant to plane more and have more breakage.
6. The first two pics show the intended fronts, which were set face-up in the mold. The next two pics show the intended backs, which were face-down in the mold. That taught me that I should have put the soap with the front facing down, because the mold bottom served to flatten out the soap face and fill in the seams a bit. That's my theory as to why the back of the soap shows a much better fit than the front. Another possibility would be to wedge something flat on the top-facing part of the soap, like a piece of cardboard perhaps.
Just my observations; YMMV. I did like my concept of a rimmed, welded soap, and I liked the look of the bars I combined. But my bad planing skills + non-softening soap left me with less than stellar results. Still, I'm glad I tried it. Good luck everyone, and I can't wait to see your entries!