macOS

pyinstaller -F -w -n ESPHome-Flasher -i icon.icns esphomeflasher/__main__.py

Windows

Start up VM
Install Python (3) from App Store
Download esphome-flasher from GitHub
pip install -e. and pip install pyinstaller
Check with python -m esphomeflasher.__main__
python -m PyInstaller.__main__ -F -w -n ESPHome-Flasher -i icon.ico esphomeflasher\__main__.py
Go to dist folder, check ESPHome-Flasher.exe works.