18650 Power pack

Hi! I'm fairly new with Arduino, and currently I still haven't memorised all of the possible power options for my projects. Recently I have been experimenting on 18650 powerpacks, some of them customized for non-arduino projects. I was wondering if my Arduino projects can be powered using a 18650 pack in a specific arrangement. I was wondering if there are any guides or diagrams for making a powerpack without having to involve a chip or an external circuit. I'm hoping to be able to power it with an arrangement similar to a 6x AA battery pack or a 9v battery adapter. Any help would be appreciated.

Also, if I am doing something wrong with this forum post, please tell me as I am not sure if I am doing it correctly.

There are 4x18650 power packs on eBay for charging phones via USB socket. Your criteria are unclear. There is no comparison with a 9v battery.

Which board? The Uno, for example, can be powered through the 2.1mm barrel jack with 6-12 VDC.