I should've been clearer. Washington and Jefferson should've did what I suggested after Britain left. There's is a huge misnomer that the the US officially got started the day after the war was won. In truth it took a few years to figure everything out from the US Constitution to setting up the three branches of government and what their duties are.
During that time the antislavery states could've pressured the other two to give up slavery in one way or another. Whether it was refusal to do trade which would break their state and local economy or a complete lockout of the nation building.