I found a way that works, but I don’t know if it’s the best practice today. This uses Bill Erickson’s tutorial. https://www.billerickson.net/building-acf-blocks-with-block-json/#script
So, script
in block.json should point to a function rather than file.
Although, now my function is in the functions.php file instead of with my block. I’m not a PHP expert so maybe there’s a way to keep this more tidy.