While I was writing my thesis I kept looking for postdoc positions in Canada. Then I found an advertisement from a lab that was similar to my Ph.D. work. I contacted the professor there and we had an interview n all that.
Then he offered me the position and based on that I applied for a closed Work permit for Canada only after finishing my PhD and getting the documents.
P.S. I did my PhD in experimental quantum physics from a reputed national Institute.