Nice projects! I use a similar sanding block:
I’d love to get another (so I could have two grits loaded and switch a bit more easily) but don’t know where to find them now. I am really happy with two features:
It grabs the sandpaper without screws or tools, it just clicks into place.
There’s a 1/4” thick firm foam pad under the paper. It’s firm enough to sand flat surfaces and has enough give to help ease corners when you want to.
I also recently bought sandpaper from amazon that is already cut to size, it’s a small thing but man is it convenient! I’m also really impressed with how durable this paper is, I’d say the sheets are lasting 3-5x as long as the other brand I was using.
320 Grit Dry Wet Sandpaper Sheets by LotFancy - 9 x 3.6" Silicon Carbide Sandpaper for Metal Sanding, Automotive Polishing, Wood Furniture Finishing, Wood Turing Finishing, Pack of 45 https://www.amazon.com/dp/B075WV9YLP