Preheat oven to 475°F. Use a paring knife to cut away the wishbone from the neck/breast area of the chicken. You will probably have to use your fingers to feel around for it. This is a little bit tricky, but if you can remove the wishbone first, it will make the chicken easier to carve after it is cooked. (This ease of future carving is the only reason to take the bone out, so you can leave it in if you want.)
Generously season the cavity of the chicken with salt and pepper. Add three of the garlic cloves and 5 sprigs of the thyme to the cavity, using your hands to rub the thyme and garlic all around the cavity.
Truss the chicken with kitchen string. To do so, start by cutting a 3-foot section of cotton kitchen string. Place the chicken so that it is breast up, and the legs pointing toward you. Tuck the wing tips under the chicken. Wrap the string under the neck end of the bird, pulling the string ends up over the breast, toward you, plumping up the breast. Then cross the string under the breast (above the cavity and between the legs). Wrap each end around the closest leg end, and tie tightly so that the legs come together.
Place the vegetables of your choice , onions, garlic, basil and remaining thyme sprig into a bowl. Add 1/4 cup of olive oil (or grapeseed or canola oil) and toss with your hands until well coated. Season generously with salt and pepper.