Iterative solution for building a BST from a sorted linked list

I want to create a BST from a sorted linked list. I solved the problem recursively, but wondered how to write an iterative solution for the same thing without changing the complexity of the problem.

[EDIT]

Note. I do not want to implement my own stack.

[EDIT2]

A function that calls itself recursively will be f. The pseudocode is given below. Call f with head pointer frommain

node * f(int start_index, int end_index, node *ptr) {
     if ( start>end) return NULL
     middle_index = start_index + (end_index-start_index)/2
     node *l_child = f(start_index, middle_index-1, ptr)
     initialize parent with ptr value 
     parent->left = l_child
     ptr = ptr->next
     parent->right = f(middle_index+1, end, ptr)
     return parent
}