**nearly chokes... ***
Uhm yeah, this isn't something you do with some wires and a few 'electronic components and software'. Cell phone and motherboard technology are created using components developed UNDER MICROSCOPES in the NANOmeter range. 'wiring' of components is done with multimillion dollar machines to achieve the 'less hair width space' line between connecting points, never mind all the IEEE requirements to meet 'standards' to ensure your electronic device doesn't interfere with other electronic devices.
In otherwords, NO you can't create your own motherboard of android phone (which I didn't' even get into the numerous differences between cellular services, signal standards, etc. in each different country or region and never mind providers). Want a crash course on 'what' a motherboard is then I would suggest first reading Encyclopedia of Computer Science and Technology page 85 and 86 CHIP, IC to CHIP and CHIPSET, then start reading all the IEEE.org standards on CPUs, Chipsets, Electronic Data Communication Switches, etc.