I know it can sound sketchy, but try craigslist. I wasn't certified yet, but I found a volunteer opportunity as a pharmacy clerk on there. I just searched for "pharmacy" under the jobs section. I found a local pharmacy that was just opening up, so they were only looking for volunteers. I found my first tech job, after got certified, on craigslist as well. There's a lot of stigma with craigslist because it's true that you never know who may be behind those ads, but I looked up the pharmacies, their addresses, and their phone numbers before I went in for interviews to make sure that they were legit.
Another great website is indeed.com. They always have postings for pharmacy jobs, but keep in mind that they are not volunteer so you would probably have to get certified as a tech first. When I was in school I also used my school's own job posting website, so if your school has one then I would highly suggest you use that.
Schools aren't necessarily looking for specific types of duties that you performed while you worked at a pharmacy. It's more about how much experience you have. Schools look for this because they don't want to waste a seat on somebody that might change their mind. If you don't have any experience, then there's the possibility that you realize half way through pharmacy school that you actually don't like the job of a pharmacist. Having plenty experience shows them that you are committed to this profession.
The best thing you can do right now to increase your chances to get pharmacy experience is to get certified as a tech. I just took the PTCB exam and then registered for a license. Even taking the test is more exposure towards a pharmacy career.