Step 1: What you will need
Karo syrup - you may substitute honey or maple syrup or pancake syrup
Rice flour - you may substitute any flour you have on hand
1 Popsicle stick
1 Mixing bowl
Amounts as follows:
2 parts Boric acid
1 part rice flour
enough Karo syrup to make a peanut butter like consistency mixture
Important note: Boric acid powder is not something you want to inhale (get into your eyes or swallow) so mix this up outside. Wear a dust mask too until it is mixed up. It has no odor.
For a 2800 square foot home with 4 bathrooms, I mixed 2 cups of boric acid with 1 cup rice powder and about 3/4 cup of Karo syrup. I used a plastic bowl to mix in and stuck the bowl and left over bait up into the attic/crawl space when I was done baiting.
*(available in hardware stores in the US as "Roach Prufe" (this was the only way I was able to buy it, the canister is 98% boric acid and 2% blue coloring).