Drill a pair of 3/8" holes in each end of the short stretchers, just over half of the depth of the dowels, using a brad-pointed bit. These stretchers already have a groove running their length, centered on the bottom edge. Precise placement isn't necessary, but keeping track of which part is which is. We need a hole in each end of each stretcher. Take care to keep these holes square, you don't want them running at angles.
Grizzly is a company currently undergoing an upheaval. This brand was once known as a manufacturer of professional grade tools and equipment for woodworking products. Though, in recent years, that reputation has begun to slip a bit since being bought by the Chinese company SIEG. These days, whether the Grizzly product stands up to its previous standards of excellence often has more to do with what you are buying than the company itself.