I start from the ends and use two or three ratcheting tie downs looped around the deck and hull to apply pressure until the deck mates to the hull in the area of the tie downs. Some gentle coaxing with a 1" putty knife can ease the narrower part outwards to meet the wider part as you ratchet them together.
Apply strapping tape across the seam to hold it tight, then release the tiedown closest to the bow or stern, move it to the next section of the seam and repeat.
Working a few inches at a time, you will tape the entire outside seam with strapping tape.
Once that is done, put the boat on edge and epoxy the downward-facing inside seam tape, let it harden, flip the boat over and do the same to the other inside seam, whereupon you can remove all the strapping tape and do the outside seams one at a time.