Simply take the 349 road between Saint-Didace and St-Alexis-des-Monts.
Nothing extraordinary to see, but not bad overall with lush trees and a really small river.
Fun slow/medium speed (40-70 kph) little road. Be careful not to go too fast in the straight sections. I almost hit a baby bear one time! If my bike broke down after, I would've had a very bad time with an angry mama bear...