Heat canola oil in a stockpot over medium-high heat. Sprinkle the pork evenly with salt and pepper. Place flour in a large zip-top plastic bag. Add pork to bag; seal. Shake to coat. Add pork to pan, and sauté 5 minutes, browning on all sides. Remove pork from the pan.
Add onion, tomatillos, chiles, and garlic to pan; sauté 8 minutes or until tender. Add pork, water, and remaining ingredients to pan; bring to a simmer. Cook 2 hours or until pork is tender, stirring occasionally.