You aren’t allowed to measure flour for baking on Yom Tov. Estimating is okay – if you use a measuring cup to spoon out the four, do not make the level even – rather the flour should be a little less or a little more heaping than the measuring cup. (ShA 1 – MB 3)
Sifting flour is not allowed even with a shinuy. You can ask a non-jew to sift with a shinuy. (ShA 2)
If you knead a batch of dough on Yom Tov, you are allowed to remove challa from it. (ShA 3)
When removing challa on Yom Tov it is tomay and therefore mutkza. But while the challa is still in your hand, you may put it down wherever you wish. Leave it there and burn it on Chol Hamoed. (MB 29)
