i achieved my “perfect” betting line by using a ruler, some painters tape, and my biggest pot. if i had a bigger one it wouldve been wider but the one i used was the biggest i could find. I started by measuring the pot diameter and found the centering point of the table. with this i marked how long i wanted my betting line with painters tape. when i was ready and everything was set I used a metallic grey sharpie to outline, i traced carefully the painters tape on the side, and using the pot I traced the end circles. I would suggest doing a light trace with something not permanent to give a better and polished look before everything is set in place, i didnt have any chalk or something like that so I just winged it but it came out nice i think.

heres a picture of what it should somewhat looklike to give u a better understanding. Also before setting anything in stone make sure all sides of the betting line are equal length space from the rail, this should help u double check everything is good