It's best if you just eat the stuff, I don't think clonazepam is very water soluble.
That said, if you are going to take something sublingually, you should be putting it under your tongue, as far back as you can, preferably beside the frenulum (little flap of tissue holding your tongue in your mouth) so as to maximize contact with the big vein on the underside of your tongue (there's one on each side of the frenulum). Not under the tip of your tongue, or to the side... Or you can take them buccally, that is, between the cheek and front of your gums - again, preferably to the back of your mouth.