HAM Ham is a very positive meat. A slice of ham can be baked in practically anything, and the thinner the slice (though not less than ¾ inch), the quicker the cooking.  Ham goes with strong spices, such as cloves, allspice and nutmeg. It responds happily to a tin of any kind of fruit juice from papaya, to guava, to peach nectar; it also enjoys a milk bath, dusted with cloves . . . or it can be combined with a tin of almost any kind of fruit (including the juice).  Pineapple is traditional but uninteresting to a gourmet; try tinned figs, or apricots, or boysenberries, or grape juice . . . or anything at all but pineapple. A slice of ham can be baked in beer or ale—or Coca Cola —but add ¼ cup of plain water to prevent any gummy residue that might toughen the ham slice.  Madeira wine and raisins go with baked ham, but otherwise a ham slice responds to few wine or butter basting sauces.  You may use a split of champagne, if you like, but all the other wines and sauces are apt to be overpowered by the salt ham taste.  Nevertheless, ham is a universal favorite—and a fine standby for the quick gourmet chef. Remember only: keep it moist, make it sweet or very plain; do not use delicate or subtle flavors in sauces because the salt in the ham will kill the taste. To serve four people, you will need a 2-lb slice of ham . . . plus whatever juices or spices you choose . . . and simply bake in a 400 oven for 30 minutes.