My kitchen sink is leaking having inspected it, I'm pretty sure it's the large black seal but I would love some insights because I like to do a job well done.
Welcome.... I'm guessing it's the gasket against the bottom of your sink???? That's your basket strainer, sounds like it's loose or worn out if it's loose you shoulder puddy the strainer and re assemble, if the gasket is worn out replace the basket strainer Assembly