Being a Wirecutter writer, I’d love to tell you that I obsessively researched the subject before building my garden beds. Why a raised garden bed? Building a raised bed allows you to create the soil mix you want from scratch. “It was also a more interesting shape, and she kinda liked that.”Here’s how to build a raised garden bed with Oldcastle blocks. Here are a few extra tips that may help improve the stability and longevity of your raised garden beds:Seat your boards.