Hi Greg,
The garden shed is a great project. I have taken the Goshen workshop as well as a Sobon workshop and each workshop uses difference methods.

Goshen used mill rule, that is every timber comes from the mill with the correct dimensions, an 8 x 8 is supposed to be 8 x 8. Goshen also used a drawing for each timber with all faces shown. However, unless you have all the drawings and a picture of the frame you won't know how the pieces are supposed to fit together or even what kind of frame your timber is for.

Sobon uses a single drawing for the entire frame and for this frame he uses square rule layout. So you need to know the basics of square rule and layout faces.

For instance in the garden shed the posts are 8 x 8's but joinery is actually cut to the perfect inner 7 x 7 timber measured from the outside layout faces. So you will need to measure your timbers and then determine if you will use 7 x 7, or maybe 7-1/2 x 7-1/2.

Assume that you use the dimensions given in Sobon's book "Timber Frame Construction". All of the information you need is there. Pictures on p. 39, 40. Plans on p. 100. Page 115 layout, drawing. P. 118 sills and post mortise. P.119, 120 drawing post top, layout face. P. 121 drawing, P 124, and 127.

The sills, posts, plates, and crossbeams are 8 x 8s. The plans show 10' from bottom of sill to top of plate. The sill is shown to be 8" high, the top of the plate is the layout face and the post top is located 7" below the top of the plate. So the post length (shoulder to shoulder, not including the tenons) is 10' - 8" -7" = 8' 9" as shown on p.120. Note: the text says to make a 2" stub tenon but you need to reduce it to 1-7/8" or so to leave a little room for cross grain shrinkage in the sill.

The plans show the longitudinal side wall girts being 4 x 4's with 5' from the bottom of the sill to the top of the girt. So the top of the girt will be located at 5' - 8" = 4'4" from shoulder on bottom of post.

Plans show 4' from the bottom of the sill to the top of the end wall section girts.

Do the same thing for the cross beams, note that the layout face for the crossbeams is the top.

The braces are shown in detail, measure 3' down and 3' over from the 7" perfect timber lines on the post and the crossbeam or plate.

I hope this is helpful, let me know if you have any more questions. I think once you have this system figured out you will like it.
Chip