Where is it leaking from?
If it is out of the place where the glass joins the barrel, then it could be a bad o-ring seal.
If it is out of the airflow holes, there are two possibilities. Is it a lot of leaking, or just a little?
If it is a lot of leaking from the airflow holes, you may need more wick to fill the wicking holes either side of the deck. Perhaps your wicking is too thin there and juice is getting past the wick and flooding the deck. You can add a bit of wick there that doesn't have to go through the coil itself, just at the sides where it passes through the wicking holes and out of the deck.
If it is just a little seepage out of the airflow holes, check your wick isn't touching the diffuser (the little cap with the holes on it) under the coil. If your coil is only a few wraps and you sent the wick straight down each side towards the wicking holes, the wick might be touching the top of the diffuser (or the air hole) under the coil and juice will then slowly seep from the wick down that central tube and out the airflow holes. The solution is to juice your wick before closing up the deck, and then put a thin (watchmakers size) screwdriver underneath the wick as you put it into the wicking hole, so you hold it away from the air intake below the coil as you train it towards the wicking hole. Raising the coil a little might help too.
So, either a bad seal on the glass, or not enough thickness of wick in the wicking holes, or the wick is touching the air intake and juice is seeping downwards, so train the wick away from the air intake and/or raise the coil a little.
As for your airflow, how about a vape band with a hole in it, to hold it in place?
