I use one of these
https://www.amazon.com/POWERTEC-71527-Flexible-Curve-Template/dp/B08LKN7H12?crid=3QIVH6GY2IX92&keywords=flexible+steel+curve+template&qid=1657426021&sprefix=Flexible+steel+cur%2Caps%2C139&sr=8-6&linkCode=ll1&tag=leftcoastcamp-20&linkId=9ec25af24310ed2a34bbc5b393a3c96a&language=en_US&ref_=as_li_ss_tl