Take the two longer pierces with the mortise holes. Push the bar into a stretcher piece - this will create a T shape.
Turn the T shape around, creating an upside-down T shape. Now, take the next longest stretcher piece pushing into the centre of the mortise hole, creating a H shape.
Take one of the two remaining stretcher pieces and push it to the next two available corners (at the top). At this stage, no need to worry about the frames being looser, as that can be tightened up with a mallet at the end.
Take the last piece, and push this into the remaining two corners, creating a two window shape.
Lastly, use the mallet on all the corners to tighten up the stretcher frame.
