To fabricate a Dutch-door, half-door, or stable-door;
You can saw a pre-fabricated solid-core (NOT hollow-core) door in half;
Or you can custom-fabricate the Dutch-door's (2)halves from:
2'x4' lumber-framing, & finished-wood paneling or plywood.
Your Dutch-door requires:
(4 or more)door-hinges(instead of 3),
(2)door-knobs/handles(instead of 1),
a door-latch (to latch bottom & top halves together).
Screens/Window(s) in the top-half are more-complicated.