These are not offcuts, they are large or small logs sliced up in the length, like bread cut lengthways.
Sometimes two adjacent slices are paired and hinged as an opening card, like a birthday card, using thin elastic cord in predrilled holes.
Perhaps one, or two long edges of any sized piece are left natural, ie side is not cut off straight but up to the surface of the log
A piece with one long straight edge as the base may suggest a Landscape drawing. Grain is often suggestive of seascape or land and sky.
If both long edges are natural then perhaps it will stand as a Portrait design.
Better pyro machines and blowtorches allow the pyrar to handle bigger pieces faster, and are less dependent on perfect surfaces. Some of my clients embellish pyro art with colour pencil or acrylic paint
Wood grain, hmm what to say, somewhere between wild to bland, light to dark, flat to warped,
Some woods twist spectacularly in drying, others hardly at all. They are stable when dry
Beginners like sycamore or birch and some folk don’t want darker woods since burns don’t stand out so well.
Some woods burn crisply: sycamore, holly, birch, lime, cherry, most fruitwoods,
while some are not so easy for a beginner but have the reward of wild grain or beautiful colour like yew or mulberry.
If your designs cover the whole wood, then plywood is good, ply birch, maple, and poplar are available untreated. If really all you want is plywood, I don’t supply it
If you want a unique tree piece, and are ready enough to let the grain be the inspiration, then try a few unique pieces or a mixed box .