Travis, I first run off a copy of the original pattern to preserve it for future use, then I select a starting point, usually a large piece in the central area of the Intarsia being worked on, and place a piece of "Clearprint 1000H Drafting Vellum" over the place on the pattern and piece I've selected to be cut. I then trace the shape of that piece on the vellum and add a line across the piece to indicate grain direction then staying outside the lines roughly cut it out and place it on the piece of wood I've selected to use for that place in the Intarsia. I use scotch tape around the whole outside piece of vellum I'm fasting to the board to prevent sawdust from getting under my pattern and then cut out the shape, cutting on the line or just on the outer edge. The first piece doesn't matter. I then select the next piece to be cut making sure it's adjoining the piece I just cut. Laying a new piece of vellum over the new area I place the piece I just cut over the pattern on top of the place where the piece would go, "If that makes sense?" I then trace that area of the cut piece that adjoins the new piece, put it off to the side and finish tracing the new piece and marking the grain direction; Remove, tape and cut, repeating for the rest of the Intarsia.
When cutting all pieces, after the first piece, I cut just on the outside edge of the pencil lines, especially where the piece will adjoin the next piece. I put little tick marks to identify those start and ending points. If anything I stay outside the lines and use one of my vertical oscillating spindle sanders to sand down to the lines. That way I always have a very tight fit. When I started out I tried cutting out all the pieces at one time and I usually ended up re-cutting pieces or living with gaps, which almost made me give up. Using the above method I hardly ever have to re-cut. When I do careless sanding is almost always the cause.
As I cut I tape all the pieces together, by putting paper masking tape on the top side of the pieces, to hold major sections together, therefore I know all pieces will match because the Intarsia is almost assembled when I'm done cutting.
I was fortunate enough to purchase several rolls of vellum when a drafting and art supply store was going out of business.
I have enough to last me the rest of my cutting days. lol
Other methods of or transferring patterns to wood are: the use of carbon paper, spray adhesive, rubber cement and etc. I find the cost of Scotch tape more than makes up for the hassle of trying to remove cements or trying to see where where the carbon transfer lines are, especially on darker color woods. I figure the time saved is worth the price of tape!
Hope this all makes sense, Al