This is one of my favorite side dishes. I'll eat these any time fresh collard greens or turnip and mustard greens are available. You can use frozen greens, but please try to get your hands on some fresh greens, they just turn out so much better in my opinion.
Using your hands, pull the leaves from the thick collard greens stems and discard the stems.
Roll the leaves lengthwise into a cigar shape, and cut crosswise into large pieces.
Fill a clean sink or a large pot with plenty of cold water, and rinse the leaves in the water, allowing any dirt or grit to sink to the bottom (repeat several times with fresh water, if necessary).
Lift the greens out of the water, and set aside in a colander to drain.
Heat the neck bones, with enough water to cover the neck bones in a large pot over medium-high heat. Bring the water to a boil, reduce the heat to low, and simmer until the neck bones are tender. This could range between 30 minutes to an hour.
Add the greens,onion,celery,bell pepper,oil and salt to the pot, stirring to combine. Cover the pot, and Continue cooking over low heat, stirring occasionally, until the greens are tender, about 45 minutes to an hour. (I do not like crunchy greens,and yes the greens will be well- cooked down, and they should be tender not stringy or crunchy.)
If the pot gets too dry, add more water as necessary to keep the greens moist(you'll want to serve the greens with a generous amount of the flavorful cooking liquid.)