Put the rice in a colander and rinse 3 times with cold water. Combine the salt, pepper, allspice and cinnamon and sprinkle over rice, stirring to mix well. Add butter and lamb to rice and mix well. Place grape leaves in a large bowl and cover with boiling water to soften. Remove and drain in colander. Cool. To stuff leaves, place a ts of the rice and meat mixture on each leaf. Beginning at the stem end, rool the leaf up over the filling, folding the sides of the leaf in, halfway toward the center, so the leaf is a nicely tucked, tight little package by the time you reach the tip. Repeat with remaining leaves and filling. Cover the bottom of a large pan with a few of the grape leaves and the lemon slices. In neat rows, arrange the stuffed grape leaves on top of the lemon slices. Invert a heavy dish on top of the grape leaves, so the bottom of the dish is pressing down on them. Add water to the pan, bring to a boil, reduce heat and simmer on low for about 35 minutes, or until stuffed grape leaves are tender.