What would be the best way to make a diamond impression on BC without an impression mat??? I wanted to try it on my moms bottom tier (birthday cake) and I didn't have enough time to get one.
You could try using wooden skewer and lay it against the crusted icing to make the indentions. I did that before I had the impression mat. You can mark off you spacing with a ruler and toothpick before you begin.
Someone else may can give you some other ideas.