I don’t recommend my method of building it yourself unless you feel confident in your bone strength and woodworking skills. But otherwise check out your local sporting goods store (Dick’s, Big 5, sportsman’s warehouse, etc.) and look for a board you like that is at least 4/5 your size (or 1/3 if you like doing things the dumb way) next just find a local place to snowboard, you will need at least a 6 in charisma for this next bit so I suggest learning how to pretend to be confident if you aren’t, you will need to talk to one of the workers there to assist you with the boots and other assorted gear if you need those. As for actually boarding: Forget how to ski, and learn to surf the snow with your balance. Knees should be bent when turning and gaining speed, when slowing stand straight and rotate hips first, keeping shoulders square. Congratulations you’re falling down the mountain in style.