Since I have moved into an efficiency apartment for the work week, I don't have internet, or cable or facebook or a TV. I am getting an amazing amount of real life things done. I have created 4 Advent Calenders, two small ones for my sweetie petie little next door neighbors and two for my older teens.
The smaller ones are 1 yard of felt, and the larger ones are a yard and a quarter of felt. The first thing you might want to do it sew the blanket binding on the edges - one pack for each calender. I learned this like most things the hard way. If you glue the pockets on first it is a very heavy and unwieldy project.
I hand drew my stockings for the pockets on heavy cardboard. I chose stockings, but I thought about Christmas Trees - It would have been hard to get goodies stuffed in the narrow tops, or round bulbs, which might have been fun to decorate but I was on a time schedule.
A little hint, when you are tracing these on felt, trace them from the back so that when you cut them out the ink doesn't show (another lesson learned the hard way).
I found on line for free a stencil for the numbers, it is a lot of numbers to cut, 1 through 25 four times. I hate the number one now. I didn't leave enough room to put the little girls names at the top, but I wanted to put my teens names on theirs. I couldn't find a free stencil for letters. I looked at the craft store, and when I finally found some about the right size, they were priced as much as the rest of my whole project, so I decided to free hand it and hope for the best.
Once you have stitched the blanket binding to the edges, hem your top and bottom. If you are going to insert a dowel to hang it from make sure your top him is wide enough to accomodate. I am hanging mine with pants hangers. I found this to be better due to the weight once they are filled.
Assuming you have cut out what ever shape you are using for pockets and numbers you can begin hot gluing.  I bought the bag of 100 glue sticks - go ahead and splurge you're going to need them. Might as well buy a box of bandaids while you are there.
If you are anal you might want to measure everything out and pin it to make sure it is straight. Or you can be like me and slap it all on there and hope its good. WARNING WILL ROBINSON: You cannot "unglue" from felt. It will rip. (once again, the hard way.)
Now comes the fun (and perhaps expensive part) Fill those pockets. If you are really generous you could get some gift cards. If you are broke like me, get a bag of Hershey Kisses (eat part yourself), some lifesavers or other individually wrapped hard candy. I splurged and bought a few special items, like a pack of pop-rocks for my son, and a few candy necklaces.

This was a fun project but plan on spending about 10 to 12 hours with all the cutting and gluing.