You remove your chicken to a serving platter/cutting board and tent (place a piece of aluminum foil lightly over it. By allowing the chicken to "rest" you are allowing the juices to seep back into the chicken and not spill out. If you cut the chicken too quickly the juices spill out leaving the meat a bit dry.
OK - now to the gravy...
Remove the chicken and place the pan on the stove. If any apple or herbs have fallen out remove them too. Turn stove to medium/medium-high. You want maybe 1/4 cup of the liquid in the pan (remove the rest but save, just in case). Now, to that 1/4 cup of liquid add about the same amount of flour. Whisk this to make a roux (pronounced rew, like flew). Keep whisking often for at least 3 minutes. You want to cook out the raw flour taste. Once 3 minutes has passed you can always cook a bit longer to give the roux some color. Once it has turned a bit browner you want to constantly whisk while you pour in some chicken broth. I will also add a bit of milk if I want a thicker gravy. This will all start to thicken quickly so you have to whisk quickly so you don't end up with clumps of flour, which in turn will create dumplings!
Just whisk fast!
Once you have the consistency you want you have gravy! Just know that if the gravy seems a bit thin it will thicken as it cools. Salt, pepper, some poultry seasoning, sage, thyme, and a bit of rosemary can always be added - - - but, your gravy will probably only require a bit of salt and pepper.