This was my first project after buying a miter saw. I used 2 inch screws to secure the back to the ledge, then nails (I think 2 inch?) to secure the front lip to the ledge. I then covered the nail holes with wood filler, painted with a white glossy paint that I had on hand for my house's trim, and secured into the wall with anchors and screws.
It was a fairly easy project and I used the cheapest wood found at home depot (each ledge literally cost less than a dollar for the wood). It did take me several hours but considering it was my first project, it was pretty fast. I'm sure someone with more experience could knock these out in 1-2 hours! It was a lot of fun and I can't wait to build something else.