I think you will find it a lot easier on your back if you build it on a set of sawhorses.  The ready made ones from the big box home center will work just fine or you can build your own following CLC's design.  Good luck to you..

http://www.clcboats.com/shoptips/stitch_glue/sawhorses_slings.html

• It was a bit of overkill, but when I asembled my Chester Yawl, I built a 16' table from two 3/4" plywood sheets (4 X 8). I built two 4 X 8 frames using 2X4X8 good quality lumber and countersunk/screwed the plywood sheets on top. I ended up with two 8' tables resting on big box store sawhorses. I joined the two with a metal brace on both sides. I sort of recall the height of the table as 36".
• That setup was wondeful: good height to work, stable and full length for the boat. I had the older kit with scarf joints, so it was great to glue the scarfs on a 16' table with the ability to create a reference line and glue all the strakes at once.
• In the end, I ended up stitching the strakes on three sawhorses as a little slack helps with the boards falling into place into the rabets. The transom is a bit fussy and I inverted the whole contraption over two aluminum ladders.
• While the table was overkill and by no means necessary, I would do it again as it proved invaluable and can be re-used for other projects. I have since hinged it in the middle, added caster wheels, two locks and a handle so that if needed I can fold it, secure it and roll it against the wall.
• I later built a cradle on casters so that the assembled hull could rest upside down on cross members. Later, I added two slings for the hull to rest right side up; This allowed me to wheel the boat in and out for sanding sessions, as well as flip it right side up or inverted by myself.