My batches generally take at least a pound of lye. My scales will measure this somewhat accurately, but it sure won't adequately measure an ounce. Do this outside. There's not too much to say about measuring the water. Get as pure of water as you can find.
Rain water is good as is distilled water.
Mix the lye in the water. Be sure to do this outside in case of spills and because of the fumes created. Always pour the lye into the water, never the other way around. The colder the water the better. Stir it with a nonmetallic spoon.