I know a PrCs can do this kind of thing, it's in MoTP but can remenber the name ! can try to find the 2nd Ed spell "Planar Seed", it can help too.
anyway as far as I remenber : this takes a long time, as upon creation the 1/2 plane is quite small and it grows very slowly.
I play a Wizard (17th Illusionist) and his friend (an arch-mage/wizard/air elementalist) are to create their own plane.... but this is to long to grow, will be dead for century before having the corrcet size ...
so by now they are looking for Time travel spell or item so we can create the plane in the past (a millenium ago) and then go back to normal time ... but still they did not found it ... (the player knows about Chronomancy spell but the character don't !!)