Flattening a binary tree into a linked list involves converting the tree structure so that all nodes follow a single path, effectively transforming it into a linked list. In TypeScript, this can be achieved using either a recursive or iterative approach. The idea is to perform a pre-order traversal of the tree and rearrange the nodes such that each node points to the next node in the traversal order. In a recursive approach, you can recursively flatten the left and right subtrees and then reattach them. An iterative approach involves using a stack to simulate the recursion process. This technique is useful in scenarios where you need to store hierarchical data in a linear format. Flattening a binary tree is a valuable skill for problems involving tree traversal and manipulation in data structures.