How do you create floating frames?

The butt joint is a very simple joint to construct. Members are simply docked at the required angle (usually 90°) and required length. One member will be shorter than the finished size by the thickness of the adjacent member. For enclosed constructions, such as four-sided frames or boxes, the thickness of the two adjacent members must be taken into consideration. For example: when constructing a four sided box made from 19mm thick material that is to be of finished size 600mm x 600mm, two of the members will be docked at 600mm and two will be docked at 600mm - 19mm - 19mm = 562mm.