Florida law requires that valid wills be in written form. Orally telling another person how one wants to legally divide one's estate will is generally not enforceable in court. Nevertheless, Floridians need to understand that merely writing the will may not be enough either. The document must meet certain legal standards, and, sometimes, a directive in the will may be found to be invalid, even if the will is otherwise properly executed.
The main case in this line of Florida law is a 1994 case called "Estate of Corbin." In this case, a will devised an estate to an individual with the caveat that the individual distribute the assets as she had been told to do by the testator, prior to the testator's death. The court found that such a bequest actually created an "oral will" that was invalid under the law.
More recent cases have, however, indicated that giving a person authority to distribute assets as that person sees fit does not create an invalid oral will. Basically, as long as the person to whom the bequest is made has the discretion of any further distribution, and is not restricted by oral instructions outside the scope of the will document itself, the will is usually valid. It is important to note though, probate courts decide based upon what a testator actually wrote, not some implied meaning, and will look only to the "four corners" of the document itself to determine what that is.
The best way to ensure that one's estate plan is carried out as one wishes it to be is to make specific bequests within the will document itself. Having competent legal advice on what is and is not acceptable in one's own specific situation may be the most important factor in determining whether the probate process is an efficient easy one, or one marred by uncertainty and conflict between loved ones.
Source: Marco Eagle, "It's The Law: Delegating distribution right under will can fail," William Morris, June 6, 2014