I bought a gravy straining jug a few years ago, the fat floats to the top then the spout pours from the bottom so you just get the meat juices no fat. This mixed with cornflour and vegetable water to make a nice thick gravy. My MIL didn’t always thicken, just an oxo cube in veg water !, the odd time she thicken it she used oxo and plain flour. When she cooked chicken she would add a chopped onion to the giblets cover with water and a oxo then cook in the oven with the chicken. Ok so far, I would then do as my mum did, strain off the liquid and thicken. Not MIL she would put the casserole dish on the table with a spoon so you could ladle the “gravy” onto your meal, it was like very greasy washing up water with giblets floating about. She wasn’t much for cooking