The patterns are linked as PDF files so that you can print each out on a standard letter-size paper in the correct size.  My hands are average size, so you can adjust yours as necessary.

Top Pattern

After gluing together, you might want to add an extra tab at the inside and outside (where the halves join) so that you can pull the Pogie on with your teeth. 
Bottom Pattern (must be mirrored along the centerline shown)

Cut out two of each piece in 1/8" neoprene, single or double-sided nylon.  I've also used 1/16" double nylon, but I don't expect it to last too long...  Both are available from Sweet Composites.

When glueing, wear thin latex gloves.  Neoprene cement tends to last a long time on the fingers.

Use neoprene cement on each of the edges, applying one or two coats (depending on how thick your cement is) and let it tack off for several minutes.  Don't glue the short sections where the paddle shaft or your hand goes through.  I do just one section of the time: First the top, then each of the sides.  

A trick I've found is to lay one piece on the other (nylon together) with the edges lined up, then squeeze short sections of the pieces together at about 1" intervals, rolling the glued edges together.  Once they are "tacked" in several places, press the entire length together.  Then turn the assemby inside-out and make sure that you have a good bond all along the seam.  I haven't found it neccessary to tape the seams.

*Note. My latest method is to glue the bottom pieces with  nylon-out on one side, nylon-in on the other.  This effectively doubles the life of the pogie if you like to have at least some of the fabric on the inside to make it easier to get the pogie on or off.

Glued edge

Both of the patterns are quite generous.  The finished Pogie will probably come further up your wrist than necessary.  You can trim them back to fit.  I usually leave "tabs" on the top and bottom of the top-hand Pogie so that I can finish pulling them on with my teeth.

Putting 'em on...

The neoprene stretches quite nicely over the T grip.  Once they are both on the paddle, I put my hand in the lower pogie, then use my teeth to pull the upper pogie over my hand.