Well, this being the 21st century, one uses a modern IDE-
https://www.sinclairzxworld.com/view...php?f=6&t=1064
It's amazing what we have these days, thanks often to the unpaid toil of enthusiasts. Just forums like this are amazing compared to the days of thumbing through magazine articles for hints and tips on technical hobbies. Datasheets a Google away, circuit simulators and, God bless us, even an advanced programming environment for the ZX81!
But we still pack our assembler into REM statements in the end...