You'll need to be at least level 10. First find the mob you want to kill and position yourself at 30 to 36 yrds (with the arctic reach talent). Then use the spell "Frostbolt" (or Ice Lance at high levels). This will snare the mob.
You then cast a second "Frostbolt" until the mob closes to within 10 to 15 yrds (with the arctic reach talent), then use your "Frost Nova" ability. This will snare the mob.
Then cast this macro:
/run FlipCameraYaw(180)
/stop casting
/cast Blink
/run FlipCameraYaw(180)
And continue casting Frostbolt. This will make it impossible to mobs to ever touch you unless they resist either a snare or nova. But if you have additional frost talents you can compensate for that.