I use a blank 75% keyboard.
For the numbers, I use F and J as points of reference to find whatever number I need. This is enough for a majority of cases, and I haven't been using a numpad for most things in the first place.
4 and 5 above F, 6 and 7 above J, 0 is 3rd from the right, 1 and 2 are two leftmost. The rest are handled by the process of elimination.
But when I need to fill out spreadsheets worth of data, I just use a Bluetooth numpad that also doubles as a calculator. For that purpose, it's just too convenient. And no, QMK layers didn't help in my case. It would help if I used ortholinear keyboard, however.