Pls see link below for days and timing for flagpoling.Would avoid the weekend. Borders are not really supposed to be used for flagpoling although you can do it. Borders often limit when you can flagpole and since it is not their primary role they can make you wait all day if they are busy. Make sure you have no other commitments that day.
https://www.cbsa-asfc.gc.ca/travel-voyage/settle-setablir-eng.html