Re-Merge El Capitan Recovery with Original Mac OS
There is not a "safe" way to do this.  Creating or destroying a Fusion Drive is a destructive process.

Having the recovery partition is normally a desirable thing, was there a particular reason you did not want it?

If you do no want to create a Fusion Drive again you will need to ensure you have a full backup.  You will need to boot from a USB installer, see here on how to create one.

If you open Disk Utility when booted from the USB installer and it detects an SSD and HDD installed it may offer to create the Fusion Drive for you automatically.  If not there are instructions here on creating one manually.

Once the Fusion Drive has been created you can proceed with the normal installation.

Note that if using Boot Camp Windows will only reside on the mechanical drive not the SSD so will not enjoy of the benefits of a Fusion Drive.  It is specified in Apple's support article.