Combine the chickpeas, 6 cups water, kombu, and 1 teaspoon salt in a large pot over medium-high heat. Bring to a boil, reduce the heat to medium-low, and cook, covered, until the chickpeas are tender, 60 to 90 minutes. Or use the Instant Pot- high pressure for 30 minutes with natural release.
Let the chickpeas cool slightly (or refrigerate up to 5 days), then drain the chickpeas, reserving the cooking liquid.
Scoop out ¼ cup or so of the chickpeas to save for garnish.
Combine the remaining chickpeas with 1 cup of the reserved cooking liquid, the remaining ½ teaspoon salt, tahini, preserved lemon, and garlic in a blender, preferably a high-powered one such as a Vitamix. Blend until smooth, adding more cooking liquid, ⅛ cup at a time, if needed to keep the mixture from stalling the blender. Continue adding liquid and blending until the mixture is creamy and light textured but not runny.
Taste and add more salt if needed.
To serve, dollop the hummus onto a large serving platter, use the back of a large spoon to swirl it around the plate, and drizzle with the olive oil. Garnish with the reserved chickpeas, preserved lemon, and parsley.
Serve with bread, pickles, and/or raw vegetables.