Open the project in Easel. Depending on the thickness of your ply and the thickness of your plane blade, you may need to adjust how many layers you need, or if you need a layer to be thinned down.
There are two outside pieces and six (two of each side) inside pieces – adjust the grey inside pieces to compensate for your blade width.
ie Blade width is 34mm, using 12.7mm ply = 38.1mm. Reduce one inside layer by 4.1mm
Set up your material and secure it tightly to the wasteboard.
Install the blade and wedge. The blade currently should not poke through, but retract it a little bit back up the plane.
Tape some 80grit sandpaper to a flat surface (a table saws cast iron surface, a block of marble, etc), and sand until the mouth opening is wide enough that you can get the blade through and the sole of the plane is flat.
Vrooooooooooooooom! Your new hand plane should be ready to go! If you want, use sandpaper or a rasp/file to provide additional smoothing to the edges, and finish it with boiled linseed oil