playing standard constructed, if my deck was 70 cards with 15 card side board in the second game could I cut my deck to 60 cards and still use my sideboard? Or because I've stated a 70 card deck does my deck always have to have that many cards in? Kind regards
Your sideboard can never contain more than 15 cards at any time, and your main deck can’t have less than 60.
So no, you can’t sideboard out 10 cards in your 70/15 deck, but you could if your sideboard started with fewer than 15 cards in it. You could even run a 75 card deck with no sideboard and just board out the worst 15 cards for games 2 and 3 of each match.












