Probably wont make much more sense with a proper photo either, but here it is, well the bits i have done, the frame and foot peg are being supplied by someone else

The 2 spacers get welded to the frame, 1 on the inside and yep, the other on the outside.
The inside spacer is drilled, tapped and fitted with an M5 grubsrew that locates a third of the way into the shank of the bolt, this stops the bolt from turning in the spacers. The bolt could have been welded to the spacers on the frame to achieve the same thing (and would have been less work for me

), but being able to remove it is probably better.
The pedal pivot then slips onto the bolt, this is wide enough to span the remainder of the bolt shank so the bearings will run on that and not the thread (although a mil or 2 over wont matter).
A 12mm threaded foot peg will then be screwed onto the end of the bolt and will trap the pivot in place.
The washer is optional and can be removed if tolerances dictate, or a second can be added.