What is the easiest edging to use around a flower bed?

Some pavers and mulch always ends up looking quite nice for a flower bed

Plastic edging kits,old bottles,broken plates.

Bottles make a great edging. Push them 1/2 way down so sun can shine through them. For a prism effect

It is according to the look you are trying to achieve. I am fortunate to live close to a good sized creek which has provided many different textured rocks of all sizes for the borders around my beds. You can also buy these type of rocks from farmers who may have a huge selection that they have found in their fields. Another place to check would be a rock quarry.

I love using bricks because they are easy to work with and you can usually get them cheaply on Craigslist, etc since you don't need huge amounts of them. They last forever, come in lots of colors and are easy to life, stack, arrange, etc.

I did used brick with mulch as there was already used brick in other hardscaping on the property when I bought the house. This way it ties all the areas together and since it is small the continuity makes it look better.