Your first step is to use a cutter that allows you to start in the middle of an area. I use my dependable Fiskar (I'll tell you how to make it dependable in another segment if you wish). I come in about 1 to 1 1/2 inches from each edge and cut to within 1 to 1 1/2 inches of each edge.
When you have cut all the way around, you can remove the center, thus:
This is your "gut" piece. Then, I do the same with my contrast color, but I cut it slightly larger (3/4 inch from each edge).
When you have both pages cut, take the border from your patterned paper, and the gut from your cardstock and overlay them. You will have about a quarter overrun on the gut for adhesive. I no longer bother drawing my cutting marks because I have done it so much I can wing it. You may want to draw out your cuts in the beginning. It's almost impossible to draw the cuts in a perfect square, but you can get close enough. When you first start, err on the side of overlap.
Personally, I don't gut my cardstock, because I seldom use it for borders. I use it for mats for pictures or journaling boxes - when I need a bigger piece, I will gut my cardstock. When you are done, this is about the amount of paper you have saved (my 12 inch ruler is on the left). Plenty to make a card, a smaller scrapbook page, or as accents for a second, facing scrapbook page.
I hope this makes sense to you. If it only adds to your confusion, leave me a comment and I'll see if I can clarify. Thanks for taking the time to stop by. I appreciate your comments, and if you have a technique or tip you want to share or need for me to find for you - let me know.
I hope you had a very Happy Easter!
Peace be the journey. Cool runnings.
Ta for now, ~ky