It is quite possible Jesus was nailed to a square piece of wood
several feet long, then this crosspiece Jesus was nailed to, was
hoisted up the trunk of a tree several feet off the ground. Then his
feet were nailed to the tree trunk.
Acts5:  30 The God of our fathers raised up Jesus, whom ye slew and
hanged on a tree.

   So, it is quite likely/ possible when they say people were hung on
a cross it means nailed to a cross-piece. Lifting up a heavy
traditional cross with a body nailed to it, so to then drop the
upright piece in a hole would have been really awkward/ difficult to
do,
     People have used the argument that since a wood plank or beam is
made from a tree, that is what was meant ???  Let's take the literal
easy to understand meaning please.
    Jesus was hung on a tree.

Lewis