First step would be to bird-proof the areas you intend to let him free-fly. Cover windows or mirrors, remove hazards, provide lots of safe landing zones. Try to look at the room from the perspective of a bird in flight. Where can he reach? What could hurt him? Don't let your bird fly in a room that isn't safe for flight.
Second step is to stop clipping his wings. He can't learn without practice. And not being allowed to fly means he is also not being allowed to develop the wing muscles necessary for controlled flight and he is not learning the practical skills that are important to using his wings to get around in a crowded indoor space. Clipped birds tend to be clumsy, poor flyers that crash a lot because they can't trust their own wings to support them reliably.
Keep in mind - just like a baby learning how to walk, you can expect that a bird learning to fly will sometimes fall. Your job isn't to stop him from ever crashing. It is to keep him safe while he learns how to fly, even if he sometimes fails to stick the landing. In time, he will figure it out. But he will need time, practice, and your support to get there.