Spray your slow cooker with nonstick cooking spray. Place ham cut side down in the greased slow cooker.
Rub 1 cup brown sugar all over the ham, then pour pineapple juice and syrup over the top.
Cook on low for 3–4 hours.
Remove excess liquid from the slow cooker and transfer to a pot. Add remaining 1–1½ cups brown sugar to pot, using more sugar if you prefer a sweeter ham. Bring to a rolling boil, then remove from the heat and pour over the ham. Cook on warm for an additional 30–60 minutes.
Remove ham to a platter. Spoon extra juices over ham slices and garnish with fresh herbs before serving.