Place the ham on a cutting board flat-side down. Make 8 to 10 deep diagonal cuts in the ham crosswise on a slight bias, about ½ inch apart. Insert the Cara Cara, blood orange and lemon slices into the cuts, allowing the tops to stick out.
Whisk together the marmalade, brown sugar, Dijon and stone-ground mustards and ¼ teaspoon black pepper in a small saucepan. Bring the mixture to a boil over medium-high heat, whisking occasionally to melt the sugar. Reduce the heat to a simmer; cook until the glaze thickens, 2 to 4 minutes.
Add ¾ cup water to the insert of a 6-quart slow cooker. Add the ham sliced-side up and brush lightly with the glaze. (Refrigerate the remaining glaze.) Cover and cook on low until the ham is hot throughout, 3 to 4 hours.
Before serving, reheat the remaining glaze over medium-low heat, stirring frequently, until simmering.
Transfer the ham to a carving platter and brush generously with the glaze until glossy and sticky. Slice and serve with the remaining glaze on the side.
