https://imgur.com/a/kEEIRhf to help visualize.
If you won't like to source all the components yourself there are vendors who happy to sell you kits, but you can make 3-5 keyboards for that amount of money.
I suggest to use the Miryoku[1] layout.
I cannot imagine using anything else anymore because it is so insanely convenient to press and hold down Capslock with my pinky finger and browse around text extremely fast.
All my keyboards also map Fn+1 to copy and Fn+2 to insert text which saves additional effort to lift my finger from Fn/Capslock.
Another combo I use sometimes is "ctrl+shift+home/end" to select the text from cursor position to the very beginning/end.
The keyboard needs to be programmable either by it's built-in firmware or by flashing a custom firmware like ZMK in the OP.
Autohotkey can do something like this for every keyboard on Windows but it's not as seamless as a firmware solution. Plus the firmware solution works on every computer you plug your keyboard into be ause it's just a remapping of the keys, not a driver hack.
So all the best wishes to the author.
But there are some tradeoffs why I probably not buy it.
1) I'd suggest a column of home/page up/page down/end (top to bottom in this order) on the right side, like some laptop makers do. They're very convenient. That's absolutely necessary for text editing or navigating in various windows. (Sure one can use combos, but then you must stick to the keyboard all the time.) Del/backspace probably also should be different keys.
2) Missing menu key also requires you to take mouse sometimes. Laptops can get away with touchpad. But with the minimal keyboard, that requires user to hold it more and use combos, you must leave the keyboard and take a mouse to open a context menu.
A general philosophical question (not a negative comment to this particular keyboard): do we really still need key rows to be shifted 1/4 of width, because keys needed arms underneath in the late 19th century?