I made a couple of photos, here is marking the tenon for drilling. The mark is about 1mm towards the shoulder from the center of the mortice bore:
After drilling the tenon, checking that every thing lines up, the view inside the draw bore:
My draw bore pins are too small, so I used clamps to get everything tight before driving the pins home. As this was a simple assembly I decided to use hide glue as well as pins. Even a simple glue up like this, just the fact of using glue kicks the stress level up the scale.
I got glue on the joints, put it together with clamps and checked that everything was square, then started driving pins home with a dead blow hammer, working around the assembly to keep it coming together smoothly. Once the pins were set pass the tenon I used a 24oz framing hammer to drive 'em the rest of the way home. I only blew up one pin, the last one and it was about 6mm from the bottom, no harm no foul. Even better, nothing moved out of square.
I'll pin the second set of legs in the AM and maybe the long stretchers in the afternoon. If not then, Sunday morning and the base will be finished.
Once the base is finished, I'll set it on the slabs and mark the mortices. It's not long before it will be upright and a working bench. My current bench will be moved against the wall and serve as an overflow work area.