Two files. One is an 11x11 grid, the other is the same grid but filled in. It's a 3mf file with the grid and fill-ins as objects so you can tweak as needed.

I always had issues with first layer evenness and adhesion on my Ender 3 S1 Pro. I picked it up used and after a few weeks I ended up with a blob of death during an overnight print. It was a mess and I tried everything from tramming to Z offset to fix my bed to correct. Despite having the CR touch sensor stock, it could never print consistently unless I printed within a 50mmx50mm area in the center of the bed. I then discovered the bed was warped like most. I took the plunge and moved to Klipper firmware to gain more granular control of the bed shape, and after a few days of testing I now have a reliable bed mesh that is working really well. I could fine tune it further, but no need for perfect just yet.

I had this grid created via Claude and it has served me very well.

Hope this helps someone else.

Realistically it can be used with any printer on Klipper with a bed mesh config. For stock firmware printers with a level sensor it is still useful to gauge where your bed level needs to be adjusted.