Add all ingredients to a pan (except the bread, clearly) and set over super low heat for about 10 to 15 minutes, stirring as necessary. You're not trying to cook the garlic, you're trying to melt the butter slowly and get it infused with the flavor of the garlic and spices.
Cut loaf of bread in half lengthwise. Using a sppon, spread your garlic butter onto the halves, being sure to cover all of the surface area with the butter and spices and garlic.
And you're all but done. When you're about 15 minutes away from wanting to serve the bread, put the bread onto a sheet pan (or cookie sheet), and into the over for about 10 - 15 minutes. Take it out when the edges of the bread are starting to brown and toast.