I do use some lump to get things started but primarily split logs. I used chunks as seen in the pics but they burn so fast I was loading the box every 15 minutes. Now, I split my logs to about the width of a beer can (which I always have one open and handy to use a measuring tool) and cut them to half length.
Karubacue inverted flame box smoker. Earthstone wood fire oven. Lynx infrared grill