An FTOS select from the GMESB is merely permission to commit to a civilian program, either by direct application/negotiation with individual programs, or via entering a binding match system.
You can (and should) talk to programs, even interview, before the GMESB meets but you can't sign a contract or verbally commit to anything.
What this means in practice is that if the FTOS select is for the very next academic year, you need to find a position in a hurry (mere months). If the FTOS is a pre-select for a later year you have a lot more freedom to find a spot and/or enter the nationwide match if one exists for the specialty.
Much of it is a frustrating exercise in flexibility and hope and some luck. But it tends to work out, once the GMESB gives the select.