Washing machine elevation, masonry, facing masonry, plinth

Good evening everyone, since the forum has already helped me so much with 2-3 other topics, I am curious about the following: I built a raised platform out of 12 cm wide bricks, where later the dryer and the washing machine are supposed to be placed. Now I originally wanted to cast the slab for the top myself, but somehow I don't like that. Can I instead use ordinary edging stones / [Mähkanten] slabs? Or does anyone have a cheap idea?

No desire for formwork and mess? Or what don't you like about it?
As it is shown in your link, it is truly ugly, but pragmatic and inexpensive. You can still make it look nice (plaster, paint, tiles, whatever)
Prefabricated lintels come to mind. But they have standard sizes and shortening them would probably be unpleasant.

Now I actually wanted to cast the plate for the top myself, but somehow I don't like it. ... Or does anyone have a cheap idea?

Everything in the picture above is just ugly. We took a wooden board and it has withstood all the spin cycles etc. for 2 years now. Simply painted white, done.

As long as the weight is not solely on the board, but as in your case also on the stones, it should work well. Thick plywood board or something like that

How does the sound behave with such a hollow body under the devices? Doesn't it resonate loudly?

How does the sound behave with such a hollow body under the appliances? Doesn't it resonate a lot?

No, although the kitchen shares a wall with the utility room, you can't even hear the machine spinning. That means we always check if the machine is finished or set an alarm directly on the oven's clock ;-) I have to add that the machine itself is not loud. And in our house, it is quiet, rarely music during the day and no TV.