I made window rest by cutting a 5” piece of 2x4 off. Then it it twice across the bottom it’s a skill saw 3 1/2” deep to fit down over window. I then glued
https://www.midwayusa.com/product/1019549984?pid=329075 to 2x4 and used it since the lat 70’s. The rest was a leather one Like in you pic. Takes about 15 minutes to build and worked great.
