Cook onion in olive oil until tender. Add rice and stir once or twice. Pour warm water and lemon juice, let it simmer, low heat. Turn off the heat after all absorbed. (You generally don't need salt, because anchovies are salty.)
Mix in greens, pepper and powdered clove.
Try your best to separate anchovies one by one without breaking. (1 small can, 2 oz, is generally good for 6 medium grape leaves)
Heap 1 tbsp mixture on each leaf, lay 1 anchovy on top of each, fold top of the leaf over the mixture, fold sides to the center and roll.
Place 1 layer of grape leaves on the bottom of a saucepan. Layer on the rolls. Put lemon slices on top of the rolls. Place a heat proof heavy saucer to prevent rolls to float. Add warm water until it is leveled with the rolls. Cook over low heat.