Trim excess fat from the ribs if necessary. Season with a little bit of salt and pepper and set aside.
Heat cooking oil in a non-stick pan over medium-high heat. Add half of the ribs and sear for 4 minutes. Flip and continue searing for another 4 minutes, or until nicely browned. Transfer the browned ribs to the slow cooker and continue browning the other half of the ribs. Transfer to the slow cooker.
Add the onions to the same the skillet. There should be plenty of oil and fat left in the pan, but if not, add another tablespoon of oil. Saute until deep golden brown, constantly stirring, about 3-5 minutes.
Add the garlic and continue cooking for another 30 seconds.
Add the water, salt, pepper and the rest of the seasonings. Bring to a simmer. Taste and adjust for salt. The liquid should be salted just right.
Pour the contents of the pan into the slow cooker over the ribs. Stir to distribute the ingredients evenly.
Set the slow cooker to low and cook for about 4-5 hours or until the pork ribs are fork-tender. You can also cook the meat on high for 2-3 hours.
Once the meat is tender, check for salt and seasonings again and adjust if needed.
If you want the liquid thickened, now is the time to do it. Carefully remove the ribs from the slow cooker and set aside. Dissolve three tablespoons of cornstarch in three tablespoons of cold water. Add the cornstarch to the slow cooker and stir well. Let simmer for about 20 minutes until desired thickness is achieved. If needed, add more cornstarch.
Return the ribs to the slow cooker and keep on 'warm' until ready to serve.
Serve with with rice, mashed potatoes, potato pancakes, pasta or other favorite side dish.