Now that I have 3 rolls under my belt, I'm going to prepare and ship off my film for scanning. My films are not as flat as they could be and I fear that my resulting scans will be of poor quality due to that fact.

What is the best procedure to make the negatives as flat as can be? I am taking my dry negatives, placing them in the plastic storage holder and then putting them under a book and then putting some weight on them (4 kg).

I just started this so I'm unsure if this will be enough.

Thanks for all the tips!