It's pretty easy. Use a front wheel motor.
https://www.amazon.com/AW-Electric-Bicycle-Powerful-Conversion/dp/B00YBWA5VC/ref=sr\_1\_3?crid=3T3XVHLX6KSP7&keywords=electric+bike+wheel&qid=1659746894&sprefix=electric+bike+wheel%2Caps%2C126&sr=8-3