Figure out how many and which pages you want to include in your book. When you are positioning the felt and items on the page in preparation to sew, make sure to leave a little bit of room on the left or right margin (depending on whether this is a front page or a back page). You are going to have to leave a little more room on the left margin if it is a front page for the eyelet holes and a little more room on the right margin if it is a back page.
Also, when you cut the muslin, cut it doubled up, so that you have identical cut pieces of material to go on the front and back (this will make it easy when you are sewing the pieces together as they will be the same size). I put little 1F and 1B marks in the corners of the pages after I cut them out, to keep them in order. So 1F stood for page 1 front, and 1B stood for page 1 Back, and then the next 2 pages I cut out were 2F and 2B and so on.
Also, when you are positioning the felt, make sure you don't put it too close to the margins. You will want to leave about a 5/8" invisible frame around the page since this frame/margin will end up on the inside of the pages when you sew the pages together.
Wait until you've finished sewing the felt onto all the pages before you begin to sew the pages together back to back. This way, if you find you need to do a bit of switching around with the pages you can. I did this a bit with my pages and tried to position them so that different things like zippers were spread out from each other or there wasn't 2 button pages in a row.
When you do begin to sew the pages together, do so by placing the finished felt sides together so that the back of the pages are on the outside. Sew a 1/2"-5/8" seam around the margins, leaving about a 3-4" opening on one of the sides (I left this opening on the margin where the eyelet holes were). Turn the pages outside in, so the right sides now appear on the outside. Press with an iron on low heat, making sure to get the edges, nice and firm (I used a bit of ironing spray to get the pages stiff). When you are sure you don't need to make any changes to the pages, then you can sew the finishing stitch on the unfinished 3-4" opening you left. Just use a simple stitch with thread similar to the muslin color. The page is now ready for eyelets.
Before placing the eyelets. Get out a piece of notebook paper and use the 3-holes as a guide so that all of your pages have equally spaced out holes helping them to fit together nicely in the quiet book and binder rings. Place the paper over the page and with a pencil, trace the circles of the holes on the left handed margin (on the front side page). You will use these marks then for putting the eyelets in the pages. Once you've put the eyelets in (3 to a page), they are ready to go in your book!