In most professional settings, meat and fish gelées are prepared—or at least begun—independently of what they will accompany, in the same way that stocks are prepared in advance and eventually used in stock-based (nonintegral) sauces or in integral sauces. Several methods can also be used to make meat or fish gelée.
The best gelées are “natural gelées” derived from the poaching or braising liquids from meat or fish. These gelées have a deep, complex flavor. However, keep in mind that stocks are essentially poaching liquids. If they are well made, from something other than just bones, they will replicate the effect of an integral sauce. In any case, start with a deeply colored and flavored liquid. To take things to an extreme, prepare a basic meat or fish broth and use it as the moistening liquid for more meat or fish. The process is repeated until the liquid contains the right amount of natural gelatin. The flavor is superlative.