I have a question that I believe would be best served with collaborative input from multiple disciplines. How can I ask a single question across more than one stack?
That's not something you should do. Each site has a specific audience so the same question is very unlikely to be answerable by multiple site audiences.
If you have a situation that may be solved by multiple sites then you should create a specific question on each of the sites, uniquely catered to that site audience.
For example if you wanted to create a fixed header on a Drupal website as part of the site template then you could ask a question on here about whether the logo should link to the homepage or not, then ask on GraphicDesign.stackexchange about what the colour combination between logo and background would be, and finally ask a question about how to integrate the template HTML/CSS into your Drupal website on Drupal.stackexchange.
The questions may all be related to the one issue that you have, but they are all separate questions so should be asked separately and to the right audience.
Further information about cross-posting questions can be found on the main meta.Stackoverflow website: Is cross-posting a question on multiple Stack Exchange sites permitted if the question is on-topic for each site?