Halve the melon and scoop out the stones. Then divide the halves again and each piece again. So basically cut the whole melon into 8ths!
Since there are also vegetarians at parties, I often serve the ham on a platter with lettuce leaves around the melon pieces. Either in the middle or around it, as you like. The ham slices are traditionally folded a little and peppered with a toothpick in the middle of the melon!