What product for levelling a windowsill?

[uluru]

We've removed a tiled windowsill and the surface left behind is rather uneven. What's the best thing to use to level it out?

 

[gregers]

er whats going back on it??.

 

[uluru]

A wooden windowsill is going on top so doesn't need to be super smooth, just level

 

[gregers]

well you could use hardwall,or fix/bond the new window board to the reveal then use expanding foam to take up the gap??

 

[uluru]

Elsewhere we've gone for the bonding and fill up the gap route but this one is sloping into the room quite a lot (the others were just a bit wavy) and I'm not sure we'd be able to fix it level without sorting out the surface a bit first.

 

[gregers]

pick the height required,and using packers then level the board when happy either gripfil the packers in place and board down onto packers or drill and screw,then foam up gap.
or hard wall and level off,when dry fit board.