Will BISSA Shoe cabinet with 3 compartments, white, 19 1/4x11x53 1/8 " fit in an Audi Q3 2019?

The Audi Q3 gives you a wide, square boot mouth: 44⅛″ across and 30¾″ tall, so most flat-pack cartons clear the opening with the seats up. Behind them the floor runs 35⅜″, and folding the rear bench stretches that to 65⅜″, a gain of 29⅞″ that turns a school-run boot into a proper load bay. The floor holds 39⅜″ across at its narrowest, so wide boxes sit flat. The catch is the lip: at 29½″ the sill is a high lift, with a 3½″ drop to the floor. Slide heavy boxes in on their edge rather than lowering them straight down.

BISSA ships as a single flat box, 54¼″ × 16¾″ × 3″, and it weighs 45 lb 15 oz. At 3″ thick it slides into gaps a built cabinet never would, so the thickness is not your problem. The length is. At 54¼″ you need a trunk that measures long enough on the floor, or one rear seat folded so the box can run forward between the seats. Most hatchbacks take it with the seats down, and any wagon or SUV swallows it flat. Lift it on edge with two hands, and rest it on a long edge rather than a corner, because 45 lb 15 oz of flat pack lands hard and the corners split first.