1. Buy BTC futures on bitmex. [If you refer to Bitmex / Deribit futures yield farming (contango market) this explains why people wants to sell their futures to you]
  2. Sell BTC Spot into stable coin (USDC for example)
  3. Then you lend out USDC on aave or comp or defi saver
    1. If the rate you lend out is higher. Then you win

By doing the above steps you essentially get borrow at 0% collateralization ratio (compare this to 150% ratio required on makerdao)