As a general rule, there is no requirement for particular formalities in trust instruments, they can be oral or written.
Once created, all questions of administration are governed by the law specified in the trust instrument.
Furthermore, the property interest need not be transferred contemporaneously with the signing of the trust instrument.
When deciding if a gift has failed, attention is first turned to the wording of the trust instrument.
All binding requirements must be contained in the trust instrument itself.
You can't know that without reading the trust instrument.
However, the Convention only relates to trusts with a written trust instrument.
It would not apply trusts which arise (usually in common law jurisdictions) without a written trust instrument.
"You never sent her a copy of the trust instrument, did you?"
Where a trust instrument runs out or is silent, the law will fill the gaps.