Others may differ, but IMO so long as the boat is square with itself it doesn't matter whether it's square with the world during construction. The forms can be adjusted with winding sticks (Nick's book shows how) regardless of whether the darned thing is level. It's just that if the strongback is level in both planes setting up the forms is easy with a spirit level. It is also a fairly easy proposition to level up the supports for the strongback so it is level, regardless of the floor. If you do level up the strongback, fasten it to the floor, or mark the position, or weight it down with sandbags or somehow prevent it from moving out of position while you're setting it up.

: Probably a silly question, but how important is it to have a level floor when
: building a strip kayak. I know that with a stich and glue this is not
: really problem, but it would seem to me that aligning strips and forms
: this would prove to be quite a challenge.

: I live in an older house and the garage floor has taken a beating with the
: shifting soils. There are some sizable cracks, but overall I would guess
: the floor rises and falls about two inches.

: Thanks

: Wesley