To make the quick pickled red onion, place sliced red onions in a bowl or glass tupperware you can store them in after. Add vinegar and salt and then add warm water until the onions are just covered. Let sit for 20 minutes before serving. You can also make these 1 or 2 days in advance and refrigerate until serving.
Arrange all of the bagel board components on a large baking sheet, board, or serving platter. Have fun arranging all the colorful ingredient... there are no rules!