Peel yams and cut into ½-inch thick slices, discarding thin ends.
Overlapping slices, arrange in a row in two shallow 9" x 13" glass pyrex dish or large baking dish, set aside.
In a small pan, combine sugar, cornstarch, and salt, stir in orange juice until well blended.
Bring to a boil over high heat and cook stirring, until sauce thickens and becomes clear (about 1 minute).
Remove from heat, add butter and orange peel, and stir until butter is melted. Pour over yams.
Bake, covered, for 45 minutes at 400 degrees. Baste tops of yams thoroughly with sauce.
Continue baking, uncovered, basting with sauce several more times, for 15 more minutes or until yams are tender when pierced.
Garnish with orange slices.