Istisna' and Making a Bedroom with Carpenter's Materials

Question:
He says: Honorable Shaykh, may Allah grant you success. A man wants to buy a wooden bedroom set. If an agreement is reached with the carpenter to make the set for a specific amount, including the carpenter securing the necessary materials, so that the man receives the set ready to use, does this fall under salam (forward sale) or under selling what one does not own, since the carpenter does not own those materials at the time of the contract?

Answer:
This is istisna', which they call istisna'. The majority of scholars hold that it is not permissible because it is selling something that does not exist yet. Only the Hanafis permit it. They call it the contract of istisna'. One person builds a building for you, provides the materials, does all the work, and hands you the key. The majority hold that this is not permissible because it is selling something that does not exist.
However, if you negotiate with him so that he does the work for you, or makes the bedroom set for you, and the materials are yours, and he only provides the labor, that is permissible and there is no harm in it. You provide the materials for him, and he does the work, and you pay him his wage for the work. That is fine. But if he is the one who pays for the materials, that is not permissible. Yes.