I was unable to find the type of base moldings that I want to use in my
house and I don't want to pay for someone to make them custom.
Essentially, all I want is flat 5" molding with an an 1/8 or 1/4
roundover on one edge. This would be complemented by a shoe mold which
I can easily find. The whole thing painted white.

Is there any reason not to get a 4x8 sheet of mdf and cut 5" strips
and use those as a base mold?

~ Wyatt