North facing flat and East facing flat is most suitable. According to Vastu Shashtra should follow the following Vastu tips :
You should build the main entrance at middle point north to north north west.
Internal parts of flat should be as the following :
|Pooja room||North East|
|Bed room||South,North,North,North West,South South East|
|Store room||North West|
|Toilet||South South West,East South EAST|