https://www.amazon.com/gp/aw/d/B07V26VM59?psc=1&ref=ppx_pop_mob_b_asin_title
This is the one I got-
I didn’t see that tip, it actually works fine when used with the flannel sheets. My method was to cut the middle rectangle then cut the 2 smaller ones to match since they are the same as the middle rectangle. The leftover I cut the big section and then used the remaining to fill the farthest forward under the sheets.
Totally works a charm and all I can say is wow, now it’s a dream to sleep on