I found looking at the coops that others had built gave me many good ideas to think about. There are some very basic plans available online to get ideas from. Here's a couple.
I spent a lot of time just looking at the coops here at BYC. Grab some tools and lumber and get to building, try not to...
Welcome! They grow extremely fast, especially the ISAs we bought. I had the coop half way done when we bought our chicks, and they still nearly outgrew the brooder before I was ready for them.