As @Dan2 says, there is lots of advice on the forum, if you search for it.
Some of the major issues:
1. Open the frame in sections, say 20% at a time. That way the honey won't flood the drainage channel.
2. Make sure the backwards tilt is 2.5 to 5 degrees - helps speed the flow.
3. Don't let the Flow tube get full to the top. If it does, you may get back pressure.
4. Don't drain uncapped frames. The cappings help to hold the honey within the Flow frame and direct it to the drainage channel
5. Don't drain into a tightly sealed container. The seal will cause back pressure as above.
There will be a lot more, but that is a summary of the most common issues I have seen.