I cut seat blanks to 3-1/2" x 2-3/4" x 3/8". The pine I had yielded 32 pieces. I'm aiming for 20 good seats so this will give me leeway. Some of them will be used up during the gutter routing process - more on this later.
A center line is added, and then the template can be used to draw the perimeter and the locations of all of the holes to be drilled except for the leg holes - again, more on this later.
The seat template never comes out symmetrical. Drawing, eyesight, transferring from paper to metal, and finally cutting the metal creates many opportunities for inaccuracies, and I seem to take at least some of those opportunities. Not to worry though, I lay the template on the wood, center line to center line and mark out one side of the center line, flip the template over and repeat for the other side.