No particular position of the hands is directed for the congregation at Mass.
For Mass with a bishop, according to Ceremonial of Bishops, n. 107 “concelebrants and ministers keep their hands joined when walking from place to place or when standing, unless they are holding something.”
A footnote to this has: "“Hands joined” means: “Holding the palms sideward and together before the breast, with the right thumb crossed over the left.” (Ceremonial of Bishops, Liturgical Press, 1989, ISBN 0-8146-1818-9, page 43)
The expression “palms sideward” is an unusual translation of “palmas extensas”, meaning “palms extended”. [The text from Caeremoniale Episcoporum (Liberia Editrice Vaticana, 1995) page 35, footnote 80: “Palmas extensas ac simul iunctas ante pectus habere, pollice dexterae super sinistro in crucis modum posito”. ] This means that the palm is to be extended, so the fingers will be extended and joined together, as well as the palms of the hands.
This general requirement to have “hands joined” by ministers does not appear in the 2002 General Instruction of the Roman Missal, so I would understand it as only applying to Mass with a bishop, following the 2002 GIRM, n. 112: " At a Mass celebrated by the Bishop or at which he presides without celebrating the Eucharist, the norms found in the Caeremoniale Episcoporum should be observed."