What role do the raised feet on the bottom of the stainless steel perforated strainer serve?

While the inside is a flat surface for holding ingredients, the four corners of the bottom are raised convexly outward.

It is raised off the surface. Because the feet are made by pressing up the stainless steel sheet itself without attaching separate leg parts, the bottom surface of the strainer does not directly touch the surface even when placed on a countertop^[1]. In general, a seamless, one-piece protruding structure prevents water stains or food residue from getting trapped in gaps, making washing and drying simple.

While it is used on its own in the sink to shake off moisture, it can also be stacked and used together with KOINU's flat-edge standard rectangular tray in XS, S, and L sizes^[2]. Placing the strainer on top of a tray allows moisture or oil drained from ingredients to drip down without getting back onto the ingredients, so you can cleanly drain moisture when scooping out freshly fried food or cooling blanched vegetables.

hmmm, rather than attaching other parts to reduce the contact area with the countertop surface, it resolved this simply by slightly pressing up a single sheet.