I smoked for years on a cheap offset and used charcoal as my primary fuel as it hated logs. I could get 5 hours out of a basket and pretty constant heat...no bad smoke or flavor either.
First, I use lump charcoal as it doesn’t have the binders and coal dust of compressed briquettes. Also burns cleaner so less dust to clog up the basket. I built a normal square basket out of expanded metal making it as big as would fit in my firebox. I never messed with a mouse-maze as I didn’t need it but hey seem to make sense if you want to experiment with it.
Now, just completely fill the basket with unlit charcoal and dump a full chimney of lit coals on top. Shut your door, close down all your air vents and give the pit an hour to come up to temp. Adjust the air vents just a little at a time and be patient as temps will take a while to adjust.
Something to remember is you have to retard the fire from the very start. If you give it too much air to get it up to temp, it will ignite the whole basket and you cannot decrease the heat at that point as your fire is a runaway. Keep it small, be patient and the temp will even out and slowly ignite new coals to maintain the steady temp.
As a side note, I have found that adding new charcoal on top of this produces bad smoke so once the basket is burned down, I just pulled it, replaced it with my second basked and dumped the first basket on top to light it.