Preheat oven to 325°. Line a 13x9-inch baking dish with aluminum foil. Pour in ¼ cup water.
Place ham in prepared pan and loosely cover with foil.
Bake on lowest oven rack until an instant-read thermometer inserted into center registers 165°, about 45 minutes to 1 hour.
Meanwhile, in a small saucepan, stir together blackberry preserves, wine, mustard, thyme, garlic, and pepper until smooth. Bring to a gentle boil over medium heat. Simmer, stirring occasionally, until thickened and coats the back of a spoon, 15 to 20 minutes. Let cool slightly.
Uncover ham and brush with half of blackberry mixture. Bake until caramelized, about 10 minutes more. Remove from oven and brush with remaining blackberry mixture. Let rest 15 minutes before serving. Garnish with thyme and blackberries, if desired.
Recipe by Southern Lady Magazine at https://southernladymagazine.com/blackberry-glazed-ham-recipe/