1. Sort all numbers
2. Build 1st BST over first half
3. Build 2nd BST over second half

Building BST like that:

For interval [l, r] make element at (l + r) / 2 the root and apply the same process recursively for left child with interval [l, (l + r) / 2 - 1] and right child with interval [(l + r) / 2 + 1, r]

If you're not required to build them and all you need is minimized maximum height, note that to minimize the height we need to make the tree a complete binary tree, and a complete binary will have floor(log₂(n)) levels assuming that a tree with a single node has height zero

If you use C++, you can calculate floor(log₂(n)) with just:

int logn = 31 - __builtin_clz(n);
int max_height = 31 - __builtin_clz((n+1)/2);