Three things cause a strapless piece to slip: wrong size, no grip, or missing structure. Fix those and it stays put through the whole night.
Size for the Ribcage, Not the Bust
A strapless top or dress needs to grip snug around the ribcage. On a strapless design like Serena's twist-knot top, if you can pull it down over your bust without unfastening anything, size down instead of relying on constant adjusting.
Grip Beats Tape
Silicone bra strips do more work than fashion tape. Tape is a good backup, not a fix for the wrong size.
Test It Before You Leave the House
Raise your arms, move like you're dancing. Whatever it does in your bedroom mirror, it'll do worse three hours into the night.
