Why not just get a platform bed frame to use now and with the memory foam too. The frame will have slats so no worries. Ikea makes lots of these that are very affordable. I have never owned a box spring and have memory foam mattresses on all our beds but they are all slatted supports.This one is from Wayfair $163.00

North America are the countries that use box springs. Which are not needed. Other countries use slats.

Slat type of support has nothing to do with airing the mattress but was just the way the box spring and mattress was held in place in "classic" bed construction.

Foam mattresses are typically not used with box springs and are used with platform style - e.g. solid surface supporting the mattress.

My current mattress is a latex foam construction (no coils but not memory foam) and I use it on an adjustable bed which is a form of solid layer support - i.e. no slats.

I can't think of a way to support a mattress without either a box spring or a solid surface of some kind - platform or adjustable type of bed frame. I suppose anything is possible but I have never seen a mattress supported by slats - the box frame provides the solid surface for the mattress and the box frame is most typically then held in the air by the slats.

I was told not to leave my new memory foam mattress on the floor for more than a week or so due to the risk of moisture coming up from below. We didn't listen, and 4 years later, the mattress still looked brand new when we finally moved it to a bed frame (with slats). (This is in the dry southwest, so I wouldn't recommend testing this theory in a humid environment.) I don't know why you wouldn't be able to put one on a solid, above-floor board.

to clarify:

I already bought a platform bed. It's from Room and Board, chosen because the the entire structure is ROCK SOLID. I had many specifications for this thing and it took months to choose something. besides the slats maybe being a tiny bit too far apart, this meets all of my other insane specs. it's really hard for me to choose furniture, I'm super picky.

according to the website, the slats are about 4-5" apart. if you look at the photo below, it looks like that's measured from mid-slat to mid-slat -- not the actual gap width. I looked at this bed in the showroom, it honestly it looks like any mattress will do fine.

so really, I'm beginning to think I might not really need a bunkie board for any mattress.

but when I AM ready to upgrade (in a few years) and the mattress company insists that the gaps are too wide, then my original question stands: is a bunkie board really that bad?

I'm old enough to remember my grandmother's feather beds. The old-school type bed frames you put boards (or slats) horizontally on top of the bed frame (the ends of the slats just sat on top of the bottom rail of the frame). Then the box spring was put on top of that, then the mattress. I suppose you could just put the mattress on it, but that was the charm of the beds - they were high and (well, as a kid) I had to run and jump on them. I suppose the slats add more support than just the frame itself. I also think that box springs add more comfort.

I prefer the modern (low profile) look of no boxspring. also, I don't like the springy effect they give. I'm a light sleeper and need something with zero bounce, otherwise my husband will wake me when he's restless. I've tested ALL the mattress types, and basically the only bed situation that will work for me is a memory foam mattress on a rock solid platform. (or separate beds, haha. don't tempt me!)

by the way, may I mention that this weirdness is personal hell for me? when we're in a guest room or hotel and it has a bouncy bed, I might not get enough sleep. :(

I have always had a slat support for my mattress no matter which one it was and no you do not need a solid base with slats. A box spring is just a box filled with springs and provide no extra comfort . The springs are there because there is no way anyone would pay the ridiculous amount of money for an empty box.

What the heck is a bunkie board?

I never said I wanted a box spring. maybe I haven't been clear enough on my original question, so let me rephrase: the slats on my bed MIGHT be about an inch too far apart per mattress recommendations, but I love this bed, it's otherwise perfect. If I put a solid plywood board under the mattress, I'm worried it'll get moldy -- some mattress sites are claiming this, but I wonder if it's just BS. my original question stands: do mattresses really need ventilation underneath to breathe? it sounds like total BS but I'm having the hardest time finding reliable sources on this.

Sammy a bunkie board is basically a sheet of plywood covered in fabric. explained here: https://purple.com/blog/bunkie-board

I have never heard that’s mattresses can’t be put on a solid surface because they need air.

Most mattresses are now placed on some form of solid surface either because people have chosen platform style beds for aesthetic design purposes or because they have opted for adjustable bed frames for comfort.