Doing a Template Tips anyone?

As I prefer custom pieces, I do my own template using clingfilm and sellotape. As I dont have anyone to assist me I usually apply the film and tape then mark it while looking in the mirror. Cut it down and double check.

At first, I use dots or hatch lines then join them up covering the area I need. The crown area is a little tricky but so far all good. In 3-years no disasters.

Usually, I do 3 attempts and pick the one Im happiest with.

Any tips for getting it right first time much appreciated.