I’ve always been able to spell pretty well---able to throw letters down in the correct sequence to form words.
Casting a spell would be a bit beyond most of us, I think, but we could all spell a word, spell out directions, or spell someone who’s plumb wore out.
In the South, you could sit a spell, passing the time of day, or rest a spell from your labors, as in “spell your tired body." In this usage, the connotations seem to be in a restful realm---you never hear anyone say “work a spell” or “cook a spell.”
There could be a sick spell, or a spell of bad weather, a fainting spell or a dizzy spell.
“Mrs. Gentry took a bad spell,” could mean myriad things---She’s really ill; she’s heard some bad news and reacted beyond the norm, or (whispered) “It’s just a matter of time.” Perhaps she’s of a certain age, and it’s just so dang HOTTT down here.
Why, everybody knows that red-headed hussy down at the truck-stop caffay spells T-R-O-U-B-L-E, and if Cissy Maud catches Bobby Frank down there one more time, she’s gonna do something that will land her a spell in the Calaboose.