Answer: Unfortunately, this is something I have never tried and I have not been able to find instructions for doing it. You might want to contact Smith and Hawkins directly and ask them how it was done.
Hyacinths may be forced in water, as may paperwhite narcissus, and the procedure is essentially to set the bulb in a container so that the base of the bulb is just barely above the water level. The roots will grow down into the water, but the base of the bulb is not in the water (to prevent rot). That would be the procedure for forcing bulbs in water in general terms. The vase needs to be heavy enough to keep the whole shebang stable when the bulb comes into bloom -- amaryllis tend to be very tall and heavy, so keep that in mind. Note, too, that these water grown bulbs are normally discarded after bloom because the growing conditions are so poor.
Amaryllis are usually planted in a pot just an inch or two wider than the bulb itself. The bulb is set so that only about half to two thirds of the bulb is in the potting soil, then watered lightly and set in a bright location at a cool room temperature. Within a few weeks they begin to come out of dormancy and send up a flowering stem, and sooner or later, foliage. Once the plant has bloomed and the flowers are fading, the stem is removed at the base and the foliage is encouraged to grow. The foliage helps rebuild the bulb's strength so it can bloom again the next year. In early fall the bulb is forced into dormancy by witholding water, and after eight to ten weeks of rest the process is begun again. In this way the bulb can be kept from year to year.
If you planted the amaryllis in soil you could certainly use an attractive cachepot to hide the utilitarian pot and still use the amaryllis as a centerpiece.
I hope this is helpful, I'm sorry I just don't know specifically about forcing them in water -- but you could certainly experiment and see if it works.
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