What are your tips on getting the SLR down?

I'm week 4 post Osteochondral Allograft (donor) of my MFC. I'm still TTWB and have only had one PT session so far. I'm progressing with flexion (AAROM) and extension but not able to lift my leg in the slightest. Quad sets are difficult- it feels like I may be compensating with my hamstring a lot. What are your tips for mastering the quad set and SLR? I'm wondering if once I can put weight through my leg it will come easier.