I use the smallest screws possible for the thickness of the word art.
To avoid splitting, pre-drill the holes from the bottom of the base into the
word art and recess the area in the base so the screws do not extend
through the bottom of the base and can strongly attach the word art.
It sounds more complicated than it is.
I put the word art on top of the base in the position I want it.
Mark the areas you want screws to go into the letters of the word art
temporarily (this can just be a small piece of masknig tape to give you a
close proximity to where the hole should be.
I drill the holes into the base, then drill a slight recess with a slightly
larger drill bit than the head of the screw. Then put the screws in so that
only a small tip of the screw point is exposed and press the word art onto the
tips of the screws. You now have an indentation on the word art that shows
where the word art has to be drilled. Of course, before drilling the base you have
to have a close estimation of where the letters in the word art should be so you
don't drill a hole in the base that does not meet one of the letters in your word art.
God Bless! Spirithorse