You CAN still do cotton outer pockets but your best bet is to make your inner something that doesn't absorb (microfleece or suedecloth). I have made 3 cotton outer pockets so far and NONE of them wick.
The way I do them is I sew the cotton fabric to the PUL at the back about 1/4 inch from the top (and I fold over the cotton fabric so it is nicely seamed KWIM?? Then I sew my elastic so that only the PUL is INSIDE the pocket. Not sure if this step is strictly necessary since my inserts don't go all the way to the top of the pocket LOL but it makes me feel more secure...
Then I sew the PUL/cotton to the fleece with good sides together...so PUL,cotton,fleece. Then I trim the cotton all the way around (again not sure if its strictly necessary since I am putting elastic on the front and legs because my pockets are side snapping...but it is working so I am not going to change it LOL!)
Then I put on the elastic and turn the diaper. I topstitch from the pocket opening to the top of the leg elastic on both sides and then topstitch the front of the pocket. I sew the elastic on the microfleece side on the legs so that the fleece rolls out (which I think provides another "layer of protection" against wicking but presenting the PUL to the insert rather than the seam KWIM??)
If you go to my photobucket
the pictures on the second row are a cotton outer pocket.