Not sure about from scratch - as I always use the pan juices not sure what you would use for flavour.
But to make from pan juices, add a bit of water to get the juices and good bits off bottom of pan - I usually put mine in a dish in the freezer for a while to set the fat and scoop it off, much healthier. Then simply mix some cornflour and water together, either microwave or put into a saucepan and do on stovetop.