I've no photo of it all attached to the #1 floorboard, but the following should get you there: The are three countersunk holes stamped into the upper plate (the one on top of the wood floorboard), one each in the corners on the left side of the plate and one in the center of the plate on the right side near the edge. All three are for #12-24 flat head screws that attach the board assembly to the leg of the firewall (the two on the left side of the plate) and the lower lip of the firewall itself (the one on the right side of the upper plate). With both plates in your hands note how the holes in the lower left corner and upper right corner of the lower plate line up exactly with the countersunk holes in the lower left corner and right center of the upper plate and at the same time all of the cutouts for the pedals and steering column line up exactly as well. This is how the final assembly will be when attached to the #1 wood floorboard with the sponge rubber weather seal between the two plates approximating the thickness of the plywood. The three little holes (originally they were smaller than 1/8") along the bottom edge of the lower plate is where tacks or nails were used to attach the lower plate to the engine compartment side of the wood floorboard so that it could all be assembled outside of the car into a whole assembly.
The remaining hole on the left side of the upper plate (not countersunk) is for the attachment of a stud (push pin) to retain the floor mat/carpeting. It is one of four such mat/carpet retainers strung along near the top of the #1 floorboard from one end to the other. The other three locations have a steel female socket inserted from the underside of the wood board into holes which are hopefully already in your board. The photos below show the sockets and the studs (one for mats and the other for carpeting) that insert into the sockets and the upper pedal plate hole in its left side. Both the female sockets and both types of push pins are difficult to come by in their original form. If you have the original #1 floorboard, likely it still has the original three female sockets intact and they normally can be removed and reused. (All three photos are from Appendix 11 of the book.)
Your sponge rubber weather seal may or may not have holes that line up with the three countersunk holes for the screws passing through the upper plate. If not, you'll have to add those holes for the screws to pass through. No separate hole in the weather seal is necessary for the mat/carpet retaining stud as they aren't very long.