Have seen these small logs at the store last couple years called a Swedish torch. Kind of neat I guess but not so neat I would pay for one. In an effort to not waste wood I made my own, sort of. Actually they are already made ! Been saving any rounds that are rotting out in the middle and using them for summer camp fires. Prop it up on a rock so air gets under and simply build a fire inside and on top by the time the fire on top burns down juts push it inside and not burns forever. This was a 18” oak round and burned ( smoldered ) for a day and a half. Nice because all the heat goes up and not so much out so kids Can do the dogs and marshmallows without getting too hot.
Neat! Make a few extra holes in the side with the saw and it should burn better. I always have the intention of doing that with hollow logs but never do!
If they are hollow all the way through I juts prop in a rock and that gets it plenty of O2 ! The ones that aren’t get a hole drilled. Works good either way. Better than sending them to the burn pile I reckon