There is an app for that :).
The app is called DiskMaker X 4b4 and was created by @liondiskmaker. The official Disk Maker X website is up and running again.
Use any of the following links to download DiskMaker X 4b4:
1. Download Link by @liondiskmaker
2. Download Mirror by @pixelgrinch
3. Download Mirror by @twoseat
All you need is DiskMaker X 4b4, the Yosemite Installer downloaded from the App store, and a USB thumb drive with 8GB or more.
Should you experience any problems, check out the Official Disk Maker FAQ page.
Sebastian mentioned in the comments that he had issues when he moved the downloaded Yosemite Installer file out of the Applications folder. For now please leave the installer where Apple downloads it to, your Applications folder.
Be aware that the content of your USB thumb drive will be erased during this process. Make sure to make a backup should you have anything important on your thumb drive.
I had a 16gb USB thumb drive on hand:
No need to worry about formatting your thumb drive in a specific format. The DiskMaker X will take care of it as long as the thumb drive is recognized by your Mac OS X installation.
- Download Yosemite through the app store. Don’t install Yosemite when the installer pops up after successful download. Go ahead and just quit the Yosemite installer.
- Launch the DiskMaker X 4b4 and select Yosemite from the first dialog box
3. The previously downloaded Yosemite installer has been placed into the /Applications directory which DiskMaker X picked up on and offers to use this copy for the bootable USB thumb drive. So let’s go ahead and use this copy.
- DiskMaker X wants to know which disk to use, so let’s use the USB thumb drive option.
- Chose your USB thumb drive from the following dialog and continue.
- A friendly reminder to make a backup of the content of your thumb drive before it is being erased.
- The following dialog brings to your attention that administrator privileges are necessary to continue.8. Enter your administrator credentials when you are asked for it.
- Don’t be alarmed if your progress bar doesn’t update the progress bar status. Be rest assured that DiskMaker X is doing its magic. This process can take some time, so feel free to grab a coffee.
- Congratulations, DiskMaker X presents its final dialog after it finished creating your bootable USB thumb drive Yosemite installer.
- The USB thumb drive has been named and formatted properly by DiskMaker X