How to Make It
Place 3 quarts water in a large stockpot; bring to a rolling boil over high, and add 1 tablespoon of the salt. Add collard greens. Cook, stirring occasionally, until greens are tender but still have a fresh green color, 10 to 12 minutes. Drain; return greens to stockpot.
While greens cook, heat oil in a medium-size heavy skillet over medium. Add 1 garlic slice to oil. Once it sizzles, add remaining garlic slices. Cook, stirring occasionally, until garlic is lightly and evenly browned and aromatic, 2 to 3 minutes. Remove from heat. Transfer garlic to a plate using a slotted spoon, and set aside; reserve garlic-infused oil in skillet.
Heat garlic-infused oil over medium-high. Add 1 bread piece to oil; once bread sizzles, add remaining bread in a single layer. (If needed, work in batches to avoid overcrowding the skillet.) Cook, undisturbed, until golden and crisp on 1 side, about 2 minutes. Turn bread pieces. Cook, undisturbed, until just golden brown on other side, about 1 minute. Using a slotted spoon, transfer bread to a plate lined with paper towels. Repeat process with remaining bread.
To serve, pour warm garlic-infused oil over greens in stockpot; toss to coat. Add vinegar, pepper, half of the reserved garlic slices (reserve the remaining slices for another use), bread pieces, and remaining 1 teaspoon salt; toss gently. Transfer to a serving platter; serve warm.