Royal Assent can be signified by one of two modes: (1) "in Parliament assembled"; or (2) "by written declaration." It was the latter mode by which Assent was signified on April 27, 2023:
On Thursday, April 27, 2023, the Right Honourable Richard Wagner, acting in his capacity as Deputy of the Governor General, signified assent in His Majesty’s name to the bills listed below. Assent was signified by written declaration, pursuant to the Royal Assent Act, S.C. 2002, c. 15....
Several justices of the Supreme Court of Canada, as well as the Secretary and Deputy Secretary to the Governor General are deputies of the Governor General:
see their commissions in The Journals of the Senate, 44th Parl, 1st Sess., November 25, 2021. (Note that their commissions currently exclude from them the power of "signifying Royal Assent in Parliament assembled," the first of the two listed modes of Royal Assent above.)
The power to appoint deputies comes from the Constitution Act, 1867, s. 14 and the Letters Patent constituting the office of the Governor General.
It shall be lawful for the Queen, if Her Majesty thinks fit, to authorize the Governor General from Time to Time to appoint any Person or any Persons jointly or severally to be his Deputy or Deputies within any Part or Parts of Canada, and in that Capacity to exercise during the Pleasure of the Governor General such of the Powers, Authorities, and Functions of the Governor General as the Governor General deems it necessary or expedient to assign to him or them, subject to any Limitations or Directions expressed or given by the Queen; but the Appointment of such a Deputy or Deputies shall not affect the Exercise by the Governor General himself of any Power, Authority, or Function.
Letters Patent, s. VII:
And Whereas by The British North America Acts 1867 [Constitution Act, 1867] to 1946, it is amongst other things enacted that it shall be lawful for Us, if We think fit, to authorize Our Governor General to appoint any person or persons, jointly or severally, to be his Deputy or Deputies... Now We do hearby authorize and empower Our Governor General... to appoint any person or persons... to be his Deputy or Deputies...
This is also mirrored in the provinces, where the Deputy Lieutenant Governor is typically the Chief Justice of the province.
Royal Assent is reported in the Canada Gazette, the official newspaper of the Government of Canada. There are many other examples of Royal Assent being signified by the Chief Justice, acting in his or her capacity as Deputy of the Governor General.