kp, this method is achieved with a small plastic retainer wall which is adhered to the floor an inch or two away from the wall with a pliable caulking type material. the bootm of the channel is the floor itself, and the other sidewall is the concrete wall. I believe it came in 4' sticks, with premolded corners and connectors, too.
It's been a while since I've seen them, but know several versions exist. I'm sorry I can't remember the brand names, but I'd check with Lowe's or other larger lumberyards. Glad I could help, best of luck!