Set your map met box like you would normally, then check 'Replace Header with Map' Under the map tab inside the map meta box.

Uncheck the display and header options inside the map meta box and make sure to check display and custom header checkboxes inside the page header meta box.

Display tab: https://cl.ly/3u0Y2q1k3s3q

Header tab: https://cl.ly/3e0p1D3S1y3p

Map tab: https://cl.ly/1I0F1q1a0w3x

Background, border, padding all unchecked.

Live demo: https://cl.ly/1s112i04002e or http://demo.themovation.com/entrepreneur/contact-2/