While I don't know anything about halibut fishing I will say that larger fluke are very lazy when compared to smaller fluke. I personally don't think a chum slick would attract big ones from a large radius. I think you're asking for a variety of trash fish to come your way more than anything.
I do think anchoring up is a great strategy to catch bigger fluke. It's better to have no drift than too much. Park yourself over a spot that you're content has bigger fish and fish both sides of the tide patiently. A wreck, small piece of structure, a specific drop off, etc. I'm actually surprised more private boats don't try this out more often when culling for quality.
