How to affix breakfast bar to top of parition half wall

Hi, If you have access underneath then you should only use a slotted angle bracket and a round head screw for fixing. (this will leave room for expansion and contraction). Be sure to choose the slot in the bracket that runs perpendicular to the width of the worktop - across the grain, not parallel to it. Plasterboard fixings such as hollow wall anchor fixings are very good. You can screw and plug from the top if access is restricted underneath. If this is the case then an oversized hole needs to be drilled and secure worktop by using a large washer and screw. Like the slotted bracket, this allows for expansion and contraction as the work surface is able to slide over the washer. Out of interest how far out does the worktop counter leave?