Here is how I build my fire in my
CharGriller offset. Like Dutch said, you need some kind of charcoal basket. I use a shaker basket made by CharBroil that Lowes carries. You need some way to raise the basket up so airflow is not restricted by ash during a long cook. I used a charcoal grate from an old grill that I bent to fit in the SFB & the shaker basket sits on top.
I am using briquettes in the pics below, but it will work with lump as well. Briquettes tend to burn longer & produce less heat than lump. OTOH, they also produce a lot more ash.
I start by filling all but one corner of the basket with unlit charcoal with 3-4 good sized chunks mixed in. I leave the front corner closest to the main chamber open to force the fire to burn back against the airflow. This seems to help slow the rate of burn
I fill a generic chimney (not as large as the Webers) about 3/4 full & get it burning good. I don't wait for all the coals to completely ash over. Just get a good fire going. I dump the lit charcoal into the open corner of the basket.
I open the stack vent & the side vent all the way. When my chamber temps hit about 210, I close the side vent down to only about 1/4 open & give it 15 mins or so to stablilze. Small adjustments to the side vent from that point will keep temps pretty stable.
When my temps drop to below 220, I shake the basket to loosen the ash & rake the remaining lit coals to the cooking chamber side & refill the basket will unlit charcoal & a few more chunks if necessary.
Hope this helps.