Trim First Side Composite Boards Flush

What happens here

Using a Makita compact circular saw (such as an 18V XSH03Z 6-1/2" model) with a guide or straight edge, carefully cut the overhanging ends of the existing composite decking boards. Position the saw blade to cut flush along the outside edge of the newly installed metal post. Make precise cuts to ensure a clean, straight edge. After cutting, remove the waste pieces of composite material.

Goal: Create a clean, flush edge on the first set of composite boards against the metal post