You mean like this, where the heel tapers down to a narrow endcap and the side is twisted to form a continuous surface rather than having a corner sticking out like usual?

I haven't made one like that myself, but I always struggle to prevent twists from developing when bending sides, so I can guess how it's done The main thing to note is that the bend radius is tighter on the fingerboard edge than the heel cap edge. So by focusing heat and bending pressure on one edge at a time, you can tighten and loosen them to induce a twist. You'll need a little extra side width since you'll end up with a corner pointing up toward the fingerboard and a corresponding gap beside the heel cap. But don't make it too wide or it will be tougher to twist, and may partially un-twist when you trim it to width, due to cutting off the fibers that were most strongly bent.

Doesn't actually help with your issue but I avoid it. Dave