I don't like to sew...I can do it, but I don't like it. I like to stay on the move, so never have been good at things that take time such as baking, quilting, crafts, etc. My daughter (just like her momma), when she was little, made me a pillow by stapling material over a ball of fluff inside (that's my girl!). You get the idea.
When I looked at those upholstered rv cushions, I knew throwing a sheet over them would look ridiculous as well as slide off. But we would never spend money on custom cushions...not our style. I thought back to the day of my daughter and her little stapler, and thought "yes!!!" - I will staple myself some new rv dining table cushions.
Here's what I did: Took off the old upholstery and threw it away. Measured all dimensions of the foam pieces (you can buy new but our foam was fine and, again, we do things for pennies). Bought 1/4" plywood pieces cut to match the 4 foam pieces. Bought $1.00/yard fabric at Walmart (thrift stores are great places to find cool fabric, too). Stretched the fabric out on a table, put the foam in the center, plywood on top of that, pulled up the sides and "zapped" with a staple gun. The End.
It was that cheap and that simple. The nice thing is if we ever get bored with it or stain it, buy a little cheap fabric and do it again!
I've listed a few items below that you will want for this job. Because my fabric was thin (and wood is sharp), I taped all edges of the wood with strong tape, to reduce the risk of ripping.