you mean with bubbles on margins? yeah its easy. just don't use a vibrator.
you mean isolated dies? not too hard.
need waxed paper and a cotton ball. wax the cotton ball over the full margin of the die, wrap the paper around the waxed cotton ball. leave as much natural tissue as possible.
carefully pour.
on harden, extract cotton ball and leave wax paper intact. pour in separate stone.
if youve done it right, the model will have wax paper separating the die and the model, making it easy to pop in and out, and easier still to keep clean. the die will need to be trimmed.