Put drained chickpeas, celery, dill pickles, vegan mayonnaise, stoneground mustard, celery seed, dried dill, and salt into a food processor. (You don't want any extra liquid around the chickpeas. So dry them off on a clean kitchen towel or really shake the colander to remove excess water before putting them in the food processor.)
Pulse the food processor until the ingredients are flaky and combined, but not to the point of becoming a creamy spread. (Occasionally stop and scrape down the sides, so that everything breaks up evenly.)
Spread additional vegan mayo onto one side of the bread slices, if you like. Top four of the slices with vegan tuna salad, and then sandwich them with the remaining pieces of bread.
Notes
If you're a fan of raw onion, add a Tablespoon or two of chopped onion into the food processor as well.If you like fishy flavors, add dulse flakes to taste.Chickpea salad sandwiches are also nice with a couple pickle slices, onion slices, spinach, and/or tomato, if desired.Other options for vegan tuna salad: put it inside a hollowed tomato, spread it onto crackers, add it as a topping for a green salad, or eat it right out of the bowl with a fork!Store leftovers in a airtight container in the refrigerator. It will keep for 3 or 4 days.No food processor? Smash the drained chickpeas with a potato masher or fork. Then add them to a bowl with the remaining chickpea salad ingredients & combine.