You may not find this method useful when you are in school, but once you are working, this can be a way to get some of what you need and an opportunity to educate about the value of user research.
When there is no research available, but you want to use "personas" as a method to help direct your design, I create what I call user "profiles".
Content is never made up, instead, it is derived from inputs from the business team (this could include someone from sales, customer service, call centre rep etc.).
It is made very clear to the business team/stakeholders that this is inferior to a true persona and that a persona is only ever based on user research. I also outline the risks and emphasize that the content is coming from their input, not from a fabrication by the design team.
This can often encourage the business team to allow you to validate the profiles with actual users to turn them in to personas. "Profiles" are also lower fidelity with less content because without input from actual users content would be limited. This can also help the business team to see where there are gaps in their knowledge about their users.
To do this, I conduct a workshop with the business team as a group. This is critical to bring about common awareness as to where they stand as a group in their knowledge.
Blank profiles are posted up on the wall (e.g. silhouette images, not faces/basic titles) the rest is blank.
Instructions, a sample and a walk through are provided as to what kind of information is expected and what kind of questions they should be asking themselves.
Everyone is provided with a set of sticky notes and a sharpie.
The group is split up into number of profiles.
Depending on the size of the group, they are given 4 - 10mins to write everything they know about a particular user and post it. Then each group rotates for another 4 - 10mins etc. until each group has had input on each profile.
Then the facilitator does a walk through of each profile to clarify any vague or confusing sticky notes.
The design team takes the inputs, does an affinity model (groups sticky notes by what they have in common) creates summaries of the content in the form of a simple persona (what I call a profile) that includes a one paragraph "story" and a user info "clouds" (think tag clouds, but for summary of user findings) e.g. "efficiency is key" "time-constrained" "brand driven" etc.
Then meet with the business team again and present the findings for further validation. This is the opportunity to demonstrate any gaps and encourage the business team to allow the design team to validate the information with end users.
Worst case, it provides the design team with some direction while providing insight to the business team as to why user research is critical.