Add the olive oil to the bottom of a 6 or 7-quart slow cooker, and top with chopped onions
Place pork roast on top of onions, then add garlic cloves to the top and inside, if the roast is tied
Season with sea salt, pepper and dried rosemary, then drizzle a little extra olive oil over the top
Cover and cook for 3 hours on high or 6 hours on low, until roast is tender and internal temperature is 150 to 160 degrees.
Mash garlic, with a fork, over the roast, then shred or cut roast into smaller pieces, and mix with the juice. If the roast is tied, remove string before shredding
Turn heat to low, and let simmer until ready to serve
Season with additional salt and pepper, if needed