Make 6 1-inch deep slits about equidistant apart along the roast and slip a clove of garlic inside (make more slits with more garlic if you like).
Place the roast in a roasting pan.
Drag out your mortar, spice mill, or sledge hammer, and crush the peppercorns along with the other 3 cloves of garlic, the salt, and the herbs and mix them into a paste (add a touch of oil if desired).
Prepare to get your hands dirty- grab some of the paste and rub it into the roast and pat it down evenly across the surface.
If you find yourself needing a bit more, make some, but this amount should do.
Cover the roasting pan with plastic wrap and marinate in the fridge 6 hours or overnight.
A few hours before you plan to start roasting, pull the roast out of the fridge and let it bring up to room temp, and let it sit that way for an hour.
Preheat your oven to 200 degrees F.
Place the roasting pan in the oven and go read a book, because this is slow roasting- at about 2 hours and 15 minutes, you might start checking on it.
You want the internal temp to come up to 110F, you should use an instant read thermometer or have had a thermometer stuck in the roast in a center part not touching the bone.
When it gets to 110F, turn the oven up to 500F- this is going to give it a fabulous crust.
Watch it closely now, and when it gets to 135F you can take it out and have a nice med-rare roast (for med, go till 150, and for well-done, go to 160).
Remove the roast from the pan and put it on your platter, but don't dare carve it for 15-20 minutes or you'll lose all the juices inside.
Degrease all the pan juices in the roaster, the add the beef stock to that, scraping up the browned bits at the bottom.
Mix the flour with the water in a small dish.
Heat the pan juices, and stir the flour slurry into it, stirring constantly until it comes to a boil and thickens.
Serve the gravy with your sliced beef, if desired.