The easiest plans would be to use a thick plywood top, a 1x4 rectangle and some 2x4 legs - use simpson strong ties for the corner pieces and it keeps everything square. You can get home depot or lowes to cut your plywood down to size before you leave the store, and you can cut the legs on the 2x4s yourself with a circular saw. The strong ties are definitely overkill but basically make it easy to get everything square without having to clamp things. They sell all that stuff at home depot.

I'd do it in two segments - one for the washer one for the dryer, and put a support leg in the middle of them depth wise - size them so you can easily slide a laundry basket under them.

There are plans on the internet where people do things with 4x4 posts and stuff but that's completely overkill for the load a washer will put on things.

I built my own this way and they have worked fine. I have been meaning to put some kind of finished facade on them but haven't gotten around to it yet.

In fact, I built mine to support that exact same 29" LG washer / dryer combo.