Are there stress marks in the plastic? if so, it's a lost cause- anything that will get the white marks out of the base will destroy the emulsion.
but, assuming the base just has a bit of a 'set' to it:
seeing as you already have it under glass, why not use a halogen worklight or something to heat it gently and evenly while the pressure is on? a piece of dark cloth as an absorber on or under the glass/film sandwich and leave it for a couple hours, and the glass (and film) should be evenly heated. The closer the light, the higher the temp. Gentle, more-or-less even, quiet, and you can go do something else while the machines do the work. . . careful not to get it too hot, as the emulsion may transfer to the glass (which it will only do UN-evenly, of course) You could do this whole heating schtick with sunlight, too, but regulating the temperature becomes a little more involved. . .
(back in my film photo days, you had to be careful drying film stock with a hair drier- you could crack or bubble the emulsion. But when you're pushing deadline with a last-minute re-shoot, well, needs must.))