How long? Hmm, as a rookie it will initially take 2 hours (1 hour each spent understanding the weave,could take a lot less depending on hand dexterity and perseverance) on the first class because we were learning to do them lol. I can give you an estimate based on my current skill, for the chainmail it might take 15 minutes to build that 1 inch by 1 inch piece, and the scale 10 minutes at most to join 6 scales (with simple rings, that piece is using coiled rings which are quite finicky to weave with so it will take longer) which would also be more or less 1 inch by 1 inch.
I actually have wanted to see how long it takes me to weave a piece, so next time I do some weaving I will make sure to record my time.
I do have to mention that there are other types of weaves which I have yet to try, Japanese (simple), Byzantine (moderate), Persian (advanced). For both those pieces I used the European (between simple and moderate difficulty) weave.