I usually start with a cold open on the plot, even if I’m going to include character customization.
I really like a creative approach to CC, and I try to add it in as naturally as possible. In one of my unpublished stories, the unseen MC slides their ID card to a bank guard across the table, then the camera zooms into the ID picture (an overlay with a duplicate character standing behind it), and character customization starts from there. After zooming out, the MC changes into the duplicate from the ID with “MC becomes DUPE,” and your character is revealed already standing in the scene as if they’ve been there the whole time.