File > New
I set mine at 10 x 8 at 240 pixels/inch.
Edit > Fill
Use any color. This is just a template.
From the ruler areas pull out guides. I set mine 1 1/4 inch in from all sides.
Using the guides, select the inner area of the rectangle using the rectangular marquee tool. Delete.
Add a new layer and using the rectangular marquee tool, select the open area of the document. Making sure you are on the new layer, fill it with a contrasting color. The color doesn't matter; you can change it when you use it. Then pull out more guides. I set mine in 1/4 inch from the existing guides. This gives me a 1 1/4 inch outer mat and a 1/4 inch inner mat. You may use different dimensions if desired.
Using the new guides make a selection inside the new color. Delete.
Using the guides again make a selection just inside the outer mat. Edit > Stroke
I used 10 px for the size and white for the color.
Click on the fx button at the bottom of the layers palette and choose either blending options. Select bevel and emboss and leave the default settings.
Do the same for the inner bevel by adding a new layer and then selecting the innermost opening and adding a stroke. Use the same settings as for the outer bevel.
Save as a .psd template
Now for some fun, let's use this template. Open the template. Select a picture you want to mat and either copy and paste it or drag it onto the template.
Resize as necessary and drag the picture to the bottom of the layers palette so it is behind the mats and bevels.
Select the inner mat (Command-click on thumbnail in the layers palette) and choose Edit > Fill
Use the eyedropper tool to select a color from the picture and choose OK. If you don't like your first choice do it again.
Do the same for the outer mat and you are done. Unless you want to change the colors chosen. Here is my finished matted picture.
Maybe that is a bit much. Maybe I like this one better.
I hope you liked this tutorial. This is meant as a guide. You could certainly make your mats of different widths and your bevels larger or smaller or whatever other changes you want.
Let me know if this works for you or if you need more clarification.