I can't remember where I saw the measurements for this enclosure. If you recognize it as yours, please let me know and I'll gladly give you the credit!
The base is Cranberry Crisp cardstock trimmed to 8.5 x 10 inches. I then scored it at 7 and then 3.5 inches (lengthways.) Figure out about where the center of one end is, then punch ONE layer with 1 1/4 inch circle punch about halfway into the punch. Do not try to punch more than one layer at once or you will ruin your punch!! How do I know this? I bent the sharp edge of my punch so that I couldn't punch it anymore! I managed to sand back the edge and it works ok now, but not as good as before. :( Once you have your first layer punched, trace lightly into the second layer and punch. Continue to the third layer. Now you can fold up your holder and tape one end and the sides together.