It needs a completely flat shelf/surface above it to screw into. Four short screws hold it in place. It’s just a titch (1/8 inch) under 30 inches wide, so if you have exactly 30 inches to fit into, it’ll go. The control panel comes out to 12 inches, flush with a standard 12-inch deep cabinet.
https://www.amazon.com/Broan-413023-Capable-Non-Ducted-Under-Cabinet/dp/B000UW20OM

