Since we are using nails to create our string art picture you may wonder why I am asking about drilling. The answer will depend on the material you are using for your baseboard. It may also depend on the size of nails you are using.
If you are using a base that is easily penetrated by nails such as cork of soft fibre board then the nails will go in easily with just a hammer. If you are using a harder base such as plywood or MDF (medium density fibreboard) then pre-drilling the holes can make the nailing easier and more accurate.
Chose a drill bit that is smaller than the nails you are going to use. You do not want the nails to fall through the holes. They should be a tight fit when nailed in.
I use a small battery powered drill. It has a built in spirit level on the top and back so it is easy to judge when it is vertical.
Fix your paper template onto your baseboard with tape or similar. Drill through the dots and then remove the template. You can now hammer your nails into the drilled holes.