A corner mounting system for self-aligning and self-leveling mounting of a mounting object in a corner between a left adjoining wall and a right adjoining wall includes: a left corner mounting device with left front and rear mounting surface; a right corner mounting device with right front and rear mounting surfaces; and optionally left and right lower support members; such that the left and right corner mounting devices can be connected between respectively the left and right adjoining walls, and left and right rear sides of the mounting object, using double-sided tape or screws, which can slide into notches of the left and right left corner mounting devices.