Landscaping - Flowerbed From Scratch

I am planning to “install” flowerbeds on the front face of my home. It is a first home (small bungalow) and the yard is wide, not deep. What I plan on doing is digging up the top turf currently covering the area I want the bed to cover then just covering it with brand mulch with built-in weed killer. The area already contains 4 round boxwoods 4-5ft in diameter.

Here is my question: When preparing the area, do I “need” the black ground-cover cloth or is this only needed in certain scenarios? I have heard other people say it’s a necessity, but I have never used it myself for any landscaping. Also, do you need to till/compost-or-resoil the entire flowerbed, or just prep the areas you plan on putting in flowers?

These are not raised flowerbeds, btw.

You don't really need the cloth, IMHO. I have had pro's do it, and the stuff only seems to last (or at least do it's job) for a year or two anyways. Weeds will normally pull out of a prepped area pretty easily anyways, or you can use chemical killers.
I'd recommend renting a tiller and do the whole area. If it's a narrow ara maybe you can rent a Mantis tiller, that's what I use. You can till in a few bags of composted manure to get the nutrients up.

Gilly

if you can cover it up, I have used newspaper with great success to help keep weeds out for 1/2 - 1 full season. Then I can just till in whats left in the fall and lay down new the next year.

It is handy because it helps with weed control but does not get in the way long-term. Just use the black and white kind and not the colored papers or anything with that "waxy" skin. Just traditional newsprint.