Rout the Post Cutout

What happens here

With the area marked, use a compact router fitted with a straight router bit to remove the material within the marked outline. Make several shallow passes with the router to gradually achieve the desired depth, which should match the height of the railing post or the desired recess. This technique prevents burning the material and offers better control. After routing the bulk of the material, use a sharp wood chisel to clean up any remaining material in the corners, ensuring they are perfectly square for a precise fit.

Goal: Create a recess in the decking board to fit around the post