Using the 12 as a set up off of the 8 is just one way I saw of getting to the BB - I see other ways of getting there as well (a lot of the shots I show will vary due to cloth speed) but I like this general pattern.
Getting the 6 off the rail is key at the beginning - I use the 1 to get on the 6.
After pocketing the 6, I want to gently come off the rail to get at the 5 in the side - there are several ways to get on the 14 next - I show a little snip shot - on second glance it looks a little off, just know that I will go from the 5 to the 14 - then I will get rid of the 14 and 8. (I was in a rush)
The key shot here is from the 8 to the 10 - you need to keep the correct angle on the 10 so you can follow to get on the 12... the only tricky part - but there is nothing too difficult in this layout.