Welcome to iboats
Find a couple of Friends with Strong Backs and Weak Minds
Secure the Trailer from Moving, unhook the winch, and pull Backwards, or secure the Stern of the boat, and pull the trailer out from under it. placing support under the hull as the trailer goes forward
In reality, a boat is only supported Ideally, when it is in the water. It is light enough empty that you really have little, if any thing thing to worry about, sitting in on the floor. Unlevel ground outside only becomes an issue if weight is placed inside the boat