Advanced feedback sandwich techniques you can use include:
Open-faced sandwiches: Start with the negative feedback, then give them positive feedback. This is great for when you are giving feedback to someone who is going to ignore the first thing you say because they already know about feedback sandwiches.
A loaf of bread: You can just tell people what is great about them. No one can stop you.
Dorito Crunch Wrap Supreme: Give them feedback while you drink Mountain Dew and snowboard.