Reply by Loren

You’ll get a more stable pillar if you “cooper” it from beveled boards.

If you cut it from a solid beam, it will surely crack somewhere. If that’s
okay with you, then go solid.

Carving such forms from solid wood has it’s own rewards, like an interesting
appearance for clear finishing, but if you’re just after the easiest, most
predictable way to make an octagonal pillar, go with the angled glue joints.