This is a great question. How do we bake bread today! The value of pre-fermented flour is a combination of flavor and digestibility. So if we want don’t have time on our side what can we do? We’ve still got to use time, but you could do a same day poolish – it is possible…
According to Modernist bread it can be ready any time between 3 and 18 hours, though an older poolish will contribute more positive effects to the dough – a better structure and more pronounced fermentation flavors. If you want to have a poolish in 3 hours you’ll need to adjust the amount of yeast to use. My rough calculations are to simply double the amount of yeast.
For a 4 loaf batch our current % of yeast as a bakers percentage to the flour (and I see there is an error on the Modern Formula that needs to be fixed) is .266%. Your target for a 3 hour poolish is 0.4-0.5% so if you use 1/2 a tsp of yeast instead of 1/4 tsp, you should be good. Be on the look out for swiftly moving dough. Manage your time by dough characteristics not by specific time.
Good luck with your bake today. Let us know how it goes.