I mostly just create the Anchor charts as I am teaching. If you feel comfortable doing the same, go right ahead. If you want to get creative, you can hop on to Pinterest and search an anchor chart for the content or book you are teaching out of and you'll see tons of creative anchor charts you can recreate with the class. If you have no desire to get creative or make one as you are teaching, I would suggest using the templates that I have created and transferring them on to the chart/poster paper. You can freehand the transfer or you can use a projector to project the template onto the chart/poster paper and transfer it that way.
Here's a quick video of what that looks like:
I would suggest using your Monday PE prep time to get this done, or any free time you have while you are on the clock and the students are away (morning, recess, PE).