The next step was to plane and thickness the components to size. Due to the dimensions, I chose to thickness the face and edge, rather than do the edge on the tablesaw.
Rinse and repeat, until I end up with all of the bottom components ready to go.
With some of the components, I could leave the central pieces long, as they will eventually form the tenons. In hindsight, however, I wish I hadn't. Unless you thickness evenly on both sides, you end up with the central piece off-centre, which makes extra work when marking and cutting the tenons. I think I'd rather have gone long on all pieces, that way I could treat it as a single workpiece when marking.
Here's the dimensioned stack. I had a little heater running in the workshop as it was bleedin' cold. It's not the greatest heater in the world, but was enough to help the glue dry as well as take the edge off when working in there.
On to marking up, and I took my time to carefully mark around all four sides and indicate waste areas. I find (from experience!) it helps avoid a lot of silly mistakes down the line.
I'm drilling out the majority of waste from the mortises with a forstner bit, so I marked and centre punched the centre of each mortise on both sides.
Over to the table saw to cut the shoulders. I first trimmed one end, and then used a stop block on the fence to help avoid any binding. I had also swapped the fence to the left side of the blade, as I hadn't yet cut the components to length and therefore couldn't reference from the other end. In hindsight, I didn't really need to do this and could have cut each component to final length - something I had to do later anyway.
Nice set of shoulders!