Clean the Swiss chard of any dry outer leaves and discard the very bottom of the stem. Cut the chard into 1-inch pieces, shredding as much of the largest pieces as possible. Bring the(and vinegar) to a boil and add the salt. Add the chard and cook 3 to 4 minutes at a simmer. When the chard is tender but still retains some of its bite, remove from the heat, drain, and shock in ice water to stop the cooking process. Drain the chard again and dry on paper towels.
In a large saute pan, heat the oil until hot, add the chard, and saute over high heat for a minute before adding the garlic and pepper flakes in quick succession. Cook the chard for 1 to 2 minutes more and then season with salt and pepper, then serve.