Sorry, that header should have read 7 *inch* wall, not foot! My bad.

well perhaps a planter .. with straight sides.. perhaps 10" deep or so..
let the planter sit on the wall with the rear of the planter along the walls surface.. and screw a strap alng the planter and straingt doen the wall.. the 3" of overhang in the front won't matter much.. infact you could go wider in the planter and overhang more.. the strap will keep it securely in place.. run the ateel strap down the planter and down the wall.. screwing it to the wall.. preferabally down a stud..and screw it in place there.. thhey make clip on brackets that hold planters.. but secureing with straps allows for more flexablity in planter types it seems to me..\ Gordon