The hands of the kohanim are washed before birkas kohanim.
Mishnah Berurah 128:21
(כא) עד הפרק - ככהן המקדש ידיו לעבודה [רמב"ם]. וע"כ כתבו האחרונים דאפשר דבעינן דוקא נטילה מכלי וכח גברא ושלא יהיו משתנים המים מברייתן ויהיה עכ"פ רביעית מים
says that the Acharonim wrote that it is possible that one needs washing from a keli etc.
In a couple of synagogues, I have seen silver vessels used which were brought to the UK by refugees from mainland Europe.
Both the silver vessels did not have a perfectly circular area from which to pour but rather had a spout, level with the rest of the vessel as in the drawing (view from on top of the vessel).
Kitzur Shulchan Oruch 40, 2 seems to exclude such a vessel (for washing for bread) when it says:
נְטִילַת יָדַיִם צָרִיךְ לִהְיוֹת דַּוְקָא מִן הַכְּלִי. וְצָרִיךְ שֶׁיִּהְיֶה הַכְּלִי שָׁלֵם בְּלִי שׁוּם נֶקֶב אוֹ סֵדֶק מְפֻלָּשׁ. וְגַם לְמַעְלָה יִהְיֶה שָׁוֶה בְּלִי שׁוּם חָרִיץ אוֹ בְּלִיטָה
Washing needs to be specifically from a vessel which should have no hole or crack and at the top should have no groove or protrusion
What then are the requirements for the vessel used to wash the hands of the kohanim before birkas kohanim?