Historical Rules · 19 November 2021
Rule 712.7
Official source text from the 19 November 2021 Rules release
If a transforming double-faced card is cast as a spell, it’s put on the stack with its front face up by default. If a transforming double-faced card is cast “transformed,” it’s put on the stack with its back face up. A player casting a modal double-faced card as a spell chooses which face they are casting before putting it onto the stack. See rule 601, “Casting Spells.”