If it is not possible to get posts down to the sill, you can settle with attaching the glulam to the surrounding studs. Partly with two sturdy angle irons at the bottom, and partly with a number of sturdy screws through the standing studs. Altogether, the screws must handle 700 kg + margin, i.e., at least 1000 kg in load across the length direction. Lag screws are probably best.
