DIY Network

I bought slats for a bench back rest and I used a drill press to start the slat wholes, I tried to clean up the holes and square the ends to accept the slats with a drexler hand held but it is coming out messy, any suggestions, can you use a mortising bit in a drill press? Any suggestions or ideas?
Thanks in advance

Get a good wood chisel or a corner chisel. Also, it helps if you make the hole slightly undersized and cut a tenon on the slats. Then the shoulder covers up any of the gaps that might occur.