First I have to say seeds and nuts is what you want for snacks. They are so light and small for the quality energy you get for long hikes!
For my sandwiches, I was a fan of bee-wax wrappers, but they are not easy to clean, and fairly messy to handle. Yes they are great for the environment, but you can not clean them hot, nor with soap which keeps bits and pieces like grease sticking to them. So I came across Lorna’s plastic wrapper that she got somewhere in XXX.
The only bad point is that it is plastic. The good point is that you can probably use it 20000 times without any problems, considering you will look after it well. It is easy to clean, with soup and hot water if you want. Easy to store and easy to wrap. On top you will have a fairly big base to put your food on like a tablecloth.