I have 3 holes in a recently skimmed ceiling which unfortunatly had to be cut out for electrics. The holes are about 6 inches in diameter. I have repaired some big holes before in walls, although not on a ceiling. I have some plasterboard, drywall adhesive and bonding plaster left over from previous work. Which is the best approach here for plastering over these holes? Should I try cutting the holes into squares and fitting plasterboard? (although not sure yet how easy it will be to cut.) Or can I keep the hole as a circle and repair it another way?