Let me walk you though steps of making corner suck pads with ruffles. This video includes a section on how to use a ruffler foot to get beautiful crisp ruffles. I even show you how to add a ribbon for double ruffles. You can always gather the ruffles if you prefer.
The pattern uses in this video is for the Kinderpack, but other 3 piece suck pads go together the same way.