Hi Samreer
Not to preempt Krileon, but since I've just done the same thing it's fresh in my mind.
I created my custom fields, and then created a user list. The area you're looking for is the Sort By section. On the line there is a drop down that lists all CB Fields, which direction they're sorted (ASCending or DESCending order) and then the "add" button which will add it to the sort list.
The problem which I believe you will have is that the hierarchy of positions is not alphabetical, so that won't work for you straight away. I'd suggest setting up a hidden field, of type integer, and create the hierarchy by assigning them each a number.
I'd also suggest separating each level of the hierarchy by 10, so you can add people inbetween easier in the future. That's a tip I've learnt about sorting that has been incredibly helpful that I wish I knew years ago.
Hopefully that helped and didn't confuse you