I just did a Bourbon Barrel Belgian Quad where I soaked 3 oz. of medium toast french oak cubes in two little bottles of Makers Mark. Let them soak sealed in a Tupperware container for about 3 weeks while the beer fermented. Threw them directly into the fermenter and let them sit for 7 days. At bottling I tasted and it had a nice subtle vanilla and oak flavor but not a whole lot of bourbon. Not sure if that will come out with some age or not.