Lay the collard green leaf flat on a cutting board. Cut the thick, tough stem away from the leaf. This means you'll need to slice a bit of the thick stem away that's located at the bottom of the collard green leaf, so you'll have a gap in the leaf. This is okay! (I prefer to cut out more of the stem because I don't like the crunch of the stem. Cutting out more of the stem does make the wrap a bit harder to roll later on.) The leaf should be able to lay flat on your cutting board once a portion of the thick stem is removed.
Add a small amount of water to a large saucepan. There should be about 1/2 inch of water covering the bottom of the pan. Heat the skillet and water just until the water begins to bubble, not boil. Place the collard green in the hot water for just about 20 seconds. The goal here is to blanch the collard green until it softens. Using tongs, remove the collard green from the water and place it on a towel. Carefully pat the collard green dry.
To close the gap in the collard green (the stem part that you sliced out), overlap the leaf to fill in the gap, creating one solid leaf. Place your filling (meat, cheese, chicken salad, sliced veggies, tuna salad) in the center of the leaf (avoid overfilling the leaf). Roll the wrap like a burrito, tucking the short ends first, then rolling the longer sides. Slice the wrap in half using a very sharp knife, or enjoy as-is as a long wrap.