Cut Opening in Roof Decking

What happens here

After removing the necessary shingles, use a 12x12 inch square template to mark the precise cut-out area on the exposed roof decking, centered on the previously marked point. With a circular saw, carefully cut along the marked lines to create the square opening. Once the cuts are complete, remove the cut-out section of plywood or OSB decking.

Goal: Create a precise opening in the roof decking for the support post to pass through.