I don't own nor have I ever used a WSM, but I do use the ring of fire method on my 22.5" OTG all the time to BBQ. With that method, I can maintain temps of ~220 for 10+ hours with no water pan. All I do is circle (with a gap) the charcoal grate with KB briquettes 2 wide and 2 high placing maybe 3-4 wood chunks along the path (including at the start). I start the ring with 4 lit coals. I leave the top vent open all the way, and leave the bottom vent open until it gets close to temp and then close it it 1/8th open.
I don't have any experience with the WSM, but I could imagine that doing something similar would probably give you at least any equally long (if not longer) burn with stead temps given how much more efficient on fuel I imagine the WSM is when compared to an OTG.
EDIT: Okay, I just realized you were asking about building a charcoal basket, not asking about the "ring of fire" method. Please ignore my post! Doh!
22" OTG; 22" Performer; mini-WSM; Brinkmann gasser; UDS (on the way); Maverick ET-732