A "standoff" is the small brass threaded piece of hardware right?
Just to clarify; I would
1. Ensure that the brass standoffs are installed on the backside of the case
2. Lay the motherboard down.
3. Fasten a metal screw through the motherboard and into the brass standoff below.
And finally, what is the rubber stud/screw type piece for... the ones that come with a new computer case?