Make a decorative cut through ham rind about 10cm (4-inch) from the shank end of leg. Make a shallow cut down centre of ham from one end to the other. Place ham on roasting rack or basket, or in a disposable baking dish. Cook ham in heated covered barbecue, using indirect heat, following manufacturer's instructions, 45 minutes or until skin begins to split. Remove from barbecue; cool 15 minutes.

To make orange glaze; stir ingredients in a small saucepan over low heat until marmalade melts.

Peel skin away from ham carefully, leaving shank end intact; discard skin. Do not cut through surface of top fat or fat will spread during cooking.

Position orange slices in a decorative pattern on ham, securing with toothpicks; push cloves into slices. Wrap shank in foil; brush ham with orange glaze.

Cook ham in covered barbecue, using indirect heat, following manufacturer's instructions, brushing occasionally with glaze, 1 hour or until orange slices are lightly caramelised and ham is heated through.