I'm certainly no master distiller, but when Maker's Mark began finishing bourbon with wood staves--by placing the same wood staves that coopers use to make barrels loosely into existing barrels of bourbon--I initially turned my nose up at the practice. It didn't seem "natural" to me. It seemed like the bourbon was somehow being adulterated. But my palate soon disabused myself of this thinking, as I loved Maker's 46.
MM has continued this practice with its Private Selection series, which uses five different staves with 1,001 different combinations. More recently, MM has introduced its "Wood Finishing Series" with one offering in each of 2019 and 2020, and two in 2021: FAE-01 in the Spring, and FAE-02 in the Fall.
I've tried (and loved) both the FAE-01 and -02; but as it's hard to find, I only own the FAE-01. The staves are French oak, with only one side charred, exposing the bourbon to both extra char and raw wood (seasoned, i.e. dried outside; not kilned) on either side of the stave.
Clear, classic tawny burnt orange color. Nose shows dried apricot, brown sugar, vanilla, buttered pancakes, raw split oak, and some ethanol (110.6 proof). Palate has a viscous, glycerin-like mouthfeel, with walnuts and oaky vanilla, finishing with leather and (still more) oaky vanilla. The oak is noticeable, but in a good way. Surprisingly little heat for the 110.6 proof.
MM FAE-01 was Whisky Advocate's #2 whisk(e)y of 2021, with a retail price of $60. Online prices currently range from $120-160.
N.B. All spirits tasted neat in a Glencairn glass.