Prep the chard stalks and leaves: Rinse out the Swiss chard leaves thoroughly. Either tear or cut away the thick stalks from the leaves. Cut the stalk pieces into 1-inch pieces. Chop the leaves into inch-wide strips. Keep the stalks and leaves separate.
Sauté garlic and crushed red pepper flakes: Heat the olive oil in a sauté pan on medium high heat. Add garlic slices, salt and pepper, and coriander seeds (if using), and cook for about 30 seconds, or until the garlic is fragrant.
Add Swiss chard stalks: Add the chopped Swiss chard stalks. Lower the heat to low, cover and cook for 3 to 4 minutes.
Add the chopped leaves: Add the chopped chard leaves, toss with the oil and garlic in the pan. Cover and cook for 3 to 4 more minutes. Turn the leaves and the stalks over in the pan.
If the chard still needs a bit more cooking (remove a piece and taste it), cover and cook a few more minutes.