Every time I have roast chicken or duck, I salvage the carcass and all the bones off everybody’s plates then boil it up with a carrot and onion to make my own stock. This also works with lamb and beef bones.
I then strain it off, leave in the fridge until it solidifies and scrape off the fat. I reduce again, so it jellifies on cooling, wrap it in cling film and stick it in the freezer.
When making gravy I always take the pan juices, discarding excess fat, add whatever vegetables (as above posts) and soften them up, THEN I add flour (enough to absorb the fat), and giving it a good cook to make a nice roux, which eliminates the floury taste.
If doing a roast dinner, I blanch all the veg in the same pan before roasting (no salt) then I melt the stock in that water. Add this bit by bit to the roux and you will have the best ever gravy. Especially if you finish it off with a bit of cabbage water.
None of your poncy wine. If you make the gravy in the meat pan, it will deglaze itself.
Oh, and it’s not that much better than making it with a knorr cube.