Considering I was pondering this question myself for the IR Aftermath PBP game I'm in here are my first choices:
Your DM may or may not allow this:
1. Get a kobold who was newly born from the mother (one who died in birth if you're a goodie two shoes), before its named
2. Live with said kobold for a few years, name it something that takes about 5 years to pronounce and is easily mispronounced.
3. Lead said kobold to a cavern, lets say 300 ft. down in the earth in the middle of no where.
4. Store your receptacle in a glove of storing, give it to said kobold to wear.
5. Cast Imprison on said Kobold.
6. Collapse cavern where you imprisoned said Kobold.
7. Forget about the Kobold.
Or, my second plan (since I'm worried about alot of divinations), is to encase the phylactery in lead and in the middle of a gigantic statue that is a gift to one of the most prominent temples of a deity, perferably one on good terms with you. You receptacle should be safe with high level clerics guarding it.
Either way, be sure to cast some protective spells, like hardening on your receptacle.