Macworld has posted an article by Albert Filice explaining how to create your own Fusion Drive from a normal hard drive and an SSD. It’s not difficult if you’re comfortable working in Terminal, but be sure you have full backups before you start, because the process will erase both drives. follow link
Open a Finder Window with the App Switcher
If you don't have any Finder windows open and want to switch to the Finder and open a window in one fell swoop, bring up the app switcher with Command-Tab and tab over to the Finder icon. While still holding down Command, press the Option key, and then release the Command key. You're switched to the Finder, with a new default window open for you.
Make Your Own Fusion Drive