Not done mine yet - mine date from 1970 and are thick vinyl, still in serviceable condition (probably good for another 40 years!) but in bright red and now looking a bit tired / faded as well as being bright red not to my taste.
Plan is to go the loose fit cover approach - given that I f##ked up my freebie domestic sewing machine
last year (3 layers of sail cloth was a test too far
) - with the backs (bottom) semi open and tensioned with elastic so fit does not have to be perfect (kinda like a fitted sheet on a bed)....instead of sewing am thinking of use plastic press studs, I feel most comfortable when using a hammer (or a close cousin
If your cushions are still servicable (and even if they need patching - as out of sight = out of mind, so matching (and neatness?!) not an issue) then maybe the same approach would work - albeit for all new (and no sewing machine) I would favour the route
mentioned by TSL - plywood
base and staples.