To build, use Visual Studio Code, install the plugin Amiga Assembly.
Find a kick 1.3 ROM and stick it in uae/rom/kick13.rom.
Use the launchers WinUAE Run ADF to run from bootblock. Debug bootblock doesn't currently work. If you want to use the external WinUAE for easier debugging, you need to edit the path in .vscode/launch.json
Disclaimer: This code is not nice. It will mug your system in a dark alley and steal both its kidneys. Never code like this unless it's for fun.