We usually make these black bean snacks from the stewy black beans (recipe also on the website). If you boil black beans just for this, add a pinch of whatever spices you want before roasting them. We like chili powder, zataar, or garam masala.
2 cups cooked black beans
Heat oven to 450F
Drain the beans from any cooking liquid and let dry at room temperature for 20 minutes or so
Toss the dry(ish) beans with a big glug of olive oil to coat
Sprinkle with salt (and any spices you want) and transfer to a baking sheet
Roast the beans in the oven until warm and crispy, about 25 minutes
Remove from the oven and let cool on the baking sheet