I'm planning on buying a laptop soon but I can't find anything with the specs that I need with an SSD. I decided to just buy one with a hard drive instead and buy a separate SSD and transfer the OS from the hard drive to the SSD. How can I use the SSD as my boot drive and leave the HDD for mass storage?
Don't transfer ("clone") the OS from the HDD to the SSD. Get yourself a Win10 install USB thumb drive by going here: https/www.microsoft.com/en-us/software-download/windows10. Take the HDD out of the laptop and install the SSD. Plug in the Win 10 install USB and start the laptop. Follow directions. Immediately after the install go to "settings->Update & security->Windows Update->Check for updates" before you do anything else.
To have HDD + SSD in a laptop you'd need either:
a laptop, that can house 2x 2.5" drives or
a laptop with 2.5" drive + dvd drive (and replace dvd drive with a caddy for second 2.5"drive) or
laptop with M.2 drive + 2.5"drive.
To transfer OS from HDD to SSD, you connect both drives to your laptop and use cloning software.