I often see this pattern on the bottom tier of whimsical cakes...large fondant diamond shapes. Sometimes it looks like the diamonds are cut out and then attached to the cake. Other times it seems like a second layer of fondant may have been placed over the cake and then the diamonds cut out. Does anyone have any advice/technique on how to make this diamond pattern? Thank you!

I have wondered that to-i do know that some people use an impression mat with a diamond pattern(i have one coming in the mail soon!)

This is how I have done it...

If you want uneven pieces (different sizes), I roll out the fondant and use a pizza wheel and just freehand it - cutting the entire piece.

If you want even pieces, I make a template with parchment paper to get the size I want, and then use a ruler to get the straight lines with my pizza wheel.

Some people do actually cut out the diamond and attach it to the cake wich has already been covered in fondant and then there is the impression mat. Hope that helps.

I guess that you are right in you first appreciation.The diamonds are cut and then attached to a previously fondant covered cake.You roll the fondant, get a ruler (or template) , and cut the diamonds the size you wish.
Hope this help.

I use the large diamond shaped cutter and I apply fondant diamonds to buttercream as well as to fondant. The look you mentioned of appearing to be diamonds cut out of the fondant covered cake is probably an optical illusion. When you attach the diamonds to the cake if you are very precise about lining them up straight and so the tips of each diamond touch it gives you that look. All the exposed white buttercream will look like diamonds as well. Here is the bottom tier of a wedding cake I have iced in buttercream and used fondant diamonds. The main thing you want to be careful of is not stretching the diamond out of shape when you lift it from the cutting board and apply it to the cake.

Thank you all so much! I will make a template and be careful not to stretch the fondant when picking it up...plenty of powdered sugar/cornstarch underneath when rolling.
Any reccomendations on where to buy an impression mat? How exactly do you use it?

I just bought one for 5.00 at country kitchen online- I think that is the name. I just did a google search for impression mats.