I'm sure that there is but I'm not sure what this type of card is called so I just winged it. I thought maybe tri-fold card but when I googled that something entirely different popped up. So... although I'm sure there are tons of tutorials for this out there, here goes one more!!
First I took my 12" x 12" paper and trimmed it to 9" x 12".
Next, I scored my paper (laid lengthwise) at 4" and 8".
After you have the 2 score lines made then take one panel and fold it forward and fold the other backwards.
For this next part you can customize it to however large you want your front panel to be. You lay a ruler in the top corner and then place the other end wherever you would like on the other end of the paper.
After you draw your line then use scissors to cut it. It wouldn't fit in my paper trimmer due to the angle which is why I did it by hand.
Once your card is cut you can refold it and use a bone folder to get good creases. Then..decorate as you see fit. Your only limited by your imagination!
Hope this helps. And, if anyone out there knows what this type of card is called please let me know!
Have a great night!