First, some details. The plane I have in mind is a low angle plane, primarily meant for use with a shooting board, but also for planing end grain freehand, with the work held in a vise. I've never had a proper shooting plane--my Stanleys aren't square enough, and my wooden planes are all 50° or higher, so not ideal for a dedicated end grain plane.
This plane will be similar to the Old Street strike block plane--it will be about 14" long with a 38° bed angle--but it will also have a 20° skew, which provides a shearing cut on the shooting board. Phil Edwards (Philly planes) makes a model like this, although his looks a bit smaller. And of course, mine will be a lefty model!
So, on to laying out the plane. This isn't really much different from laying out a "normal" plane. I always start by laying out one side. From left to right, we have the bed, the blade, the wedge, and the front of the throat.
With a "normal" plane, I would then transfer these marks across the sole with a square, lay out the other side, then transfer those marks across the top. If I don't end up back where I started, something went wrong, so I go back and find the problem.
So, for this plane, I do the same thing, just using a bevel set at 20° instead of a square.
The layout on top isn't quite complete--the throat has to flare out so that it's the same width at the front as at the rear. But that's later. The initial focus is on making a trough that is about 1/2" narrower than the iron.
The final layout task, for now, is to mark some locations for drilling. I scribe a bunch of lines parallel to the skew angle, in white pencil so I don't confuse myself. Then I punch centers for drilling.
The basic idea is that all points on a white line will have the same final depth, so I can drill 3 holes before I have to change the depth stop on the drill press. This process is time consuming, but makes chopping the mortise a lot easier.