There are some amazing quiet book inspiration pages out there and I have a whole Pinterest page dedicated to it. You'll also find a lot of blogs with instructions or whose sole purpose is the quiet book. I found one such blog that had fun templates like a Mr. Potato Head activity page. I decided that seemed pretty simple and would be a good starting point.
You can get the templates to make your own Mr. Potato Head quiet book pages here. Once I downloaded the templates, I cut out the various pieces to assemble my quiet book. I ordered my felt from Etsy - I found they had the greatest selection of colors to choose from and reasonable prices.
I also have a very extensive collection of embroidery thread. This isn't even the full amount - I have a lot pulled aside for current embroidery projects. I used a combination of hand-stitching with embroidery threads (especially on the small pieces) and my sewing machine on the large pieces.
I made a whole bucket of various pieces to attach to Mr. Potato Head. They all get stored in the bucket and Ian can pull them out and piece them on to the potato in whatever way he chooses.