What are some ways to invest with zero commissions or fees?

What are some ways to invest with zero commission/fees? I have money in robinhood, I bought some bonds through treasury direct, I have a little bit of passive income going into a sallie mae money market account at 1.5%, and I'm considering doing a student account on stash... but what I want to know is, what are some other ways to do commission free/zero fee investing? I'm looking to create an entire portfolio that I don't pay any commissions or fees on. Any more ideas? Brokers, sites, apps, tricks, tips, coupon codes?
Asked Jun 27, 2016

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