How programatically cause uploads folder to be created?

This should work – using wp_upload_dir to get the path, then checking to see if it exists – and creating it if it doesn’t.

$upload_dir = wp_upload_dir();
if (!is_dir($upload_dir['path'])) {  // directory doesn't exist
    mkdir($structure, 0744, true); // the mode to use here may vary based on your hosting environment
}