Traditionally, sasae-tsurikomi-ashi is done from the sleeve side. It does work that way but the lapel side offers a stronger pull and the target leg is nearer to tori's attack leg.

To generate the momentum for the throw, tori does a little twitching action, as if going for an osoto-gari, harai-goshi or uchimata, and then spins uke around for the throw.