Rinse oysters well. Using a tea towel, grasp oyster in one hand, cup-side down. Insert the oyster knife into the hinge and use a twisting motion to separate the top and bottom shells. You should feel the hinge pop when you twist the knife.
Run the blade along the top of the shell to separate the top and bottom shells. Open the oyster, taking care to hold it level so the brine doesn't leak out.
Wipe away any bits of shell with a finger. Set oysters on plates with lard. Serve with lemon slices and whole grain bread, if desired.