I have a baseboard heater in my kitchen. The thermostat that controls that heater is on part of a wall that is being taken out. I would like to move this thermostat. Where I want to move it, I don't have enough wire, and it would be way too difficult to run a new wire. I would like to place a junction box (that would be accessible) right around it's current location and then run a wire from the junction box to the new location for the thermostat.
I think I could figure this out... but.. I never know if what I'm doing it the "correct" way. I would like to be as correct as possible.

So.. here is the deal. Currently I have three 12-2 lines coming into the current thermostat fixture box. One line is the power coming into the box from breaker. One line is the one that runs back to the baseboard heater, and the last wire seems to be going on to the next room to supply power to that heater.

Here is how they are currently wired together in the box. All WHITES are nutted together. The BLACK wire from the line that goes to the baseboard heater is screwed into one of the terminals of the thermostat. The BLACK wires from the power feed line and the line that goes goes on to the next room are nutted together and then pig tailed to the other terminal on the thermostat.
What is the correct way to junction this and then wire up the thermostat in its new location?

Thanks in advance for your help!

Run 12-2 cable new location.
Remove pigtail and connect white of new cable.
Connect to black of new cable.

At new location connect white and black to thermostat terminals.

HKSTROUD.. I'm just now wiring up the jbox the way you suggested.. and that makes perfect sense... thank you. I do have one more question. I ran the 12-2 cable from jbox to new thermostat location... however... I don't know what to do with ground cable. I put in a plastic box for the thermostat.. and the thermostat does not have ground terminal..
Do I have to put in a metal box? I'd rather not.. but will if I have to. Thanks!

No, if you are using a plastic box and the thermostat does not have a ground connection, just wrap ground wire around sheathing of cable. And that is just in case you need it later.
Otherwise just clip it off.

As always.. thank you very much!

I am wondering just where the junction box is going to be.

I'm taking out a pantry that is like only 13" deep so I can just put cabinets there.. to give it a cleaner look. The thermostat was on one of the side walls that needed to be cut back 13". The cabinets are going in where the pantry was. Cabinets are 84" high. So with the extra foot over the cabinet I'm just going to put the junction box there so it's accessible but really not able to be seen since it's so high above the cabinets.
Is there a problem with this that you're wondering about where the jbox will be?