Spine Flexibiltiy and Bench Press Arch

I am looking for any advice/suggestions on how I can increase my
spine flexibility and Range of Motion to develop an arch in the bench
press. I am would like to switch my style to the arched style but I
am combating a lack of spine flexibility. Bottom line - my spine is
stiff as board when I try to arch. I have tried to research this
issue but I have not had much success. I realize that I may never
achieve a Lamar Gant type of arch but I believe there has to be a way
to attain my maximum ability to arch. I welcome any and all suggestions.>

try rolling your back on a swis ball. maybe you need a trip to a chiropracter or art specialist. even a massage therapist might work. don’t know anybody who couldn’t arch some.