I was recently asked how to make conference presentations more accessible to Deaf/hard-of-hearing attendees. Now, I have written a guide on that, but I'd like to broaden the question to include other forms of conference access. There are a number of good guides out there, so I'm not going to rehash them; instead, I will link to some of them.
Two more notes here - first, at least for my field (engineering education), I think the real question will be not so much how willing a conference is to enforce some of these things (either through requirements, design, or likely some combination or the two) as opposed to simply suggesting them as nice things for attendees to do. Quite frankly, if people don't have to do these things... many don't. A lot of them require advance planning and other aspects that are not part of academic conference presentation culture by default (finishing your slides before the day you present them? what?!!?)
Second, although the guides above focus mostly on disability-related access, remember that there are other forms of access and inclusivity that are important, too. Is your event affordably priced and/or does it have scholarships available? Is it at a location that is easy to travel to, stay at (are there wheelchair-accessible lodging options that aren't super expensive?), eat at (will those with food allergies and vegans/vegetarians be able to find options)? Is it at an hour where people with day jobs and/or small children can attend? Is there childcare? A quiet room? Gender-neutral restrooms and buttons/stickers with different pronoun options? A code of conduct and the means to enforce it? Are you deliberately soliciting participation from a wide variety of people? There are a lot of ways to make events inclusive!
I'd also like to note: conference access is not my specialty, nor is it my area of expertise. I love conference planning, but I'd rather be on the program committee, etc. than the "diversity and access" board. In order to do this, other people need to do the diversity and access work, because I literally cannot participate in the conference without it. Until I'm able to completely trust it'll be there regardless of what I do, I won't be fully able to do other things. So. Please do this work so I can be on program committees and other stuff instead! Please.