You can visualise someone on top, like a cowgirl or whatever suits your imagination.
With your stomach downwards, you can stimulate yourself against the pillow bump which is squishy yet elevated, perfect for your pleasure.
If you can then you are in for a very interesting and fun, solo time.
But did you know that there are a few more positions that can take your masturbation game to another level? You can sit on with your legs spread, bend backwards until your head is on the floor put a pillow or mattress for supporting your head if you want.
No it is not just the visuals in your head that can get dirty but also how you go about it matters.