Your secret to making your cards very flat?

joblackford, if I understand Correctly she is speaking about cards that she’s purchased and held in her hands.

Perhaps it’s the CS you use FurryP? I use Hammermill 100lb and of I take the few extra seconds to really burnish the fold I can get a very flat card. So maybe experiment with different cardstock?

Oh, OK, got it. I was thinking about cards you'd seen photographed! 
When I sold cards they got made months (or years 😬 ) before they get sold and I kept them stored in little plastic sleeves during that time - helped flatten them out a lot. 

I feel like some of the things that can help like using a lighter weight of cardstock or scoring deeply can also work against the durability of the card. I've busted through the cs with my bone folder plenty of times. And of course you don't want to/shouldn't buy new cs when you already have plenty.

The other thing I would check is whether your score is on the correct side of the fold - the "mountain" side of the score should be inside the card. Does that make sense? I think I was doing it the wrong way for a long time. 

Good suggestions so far. I would add that you should also make sure that the adhesive you're using isn't warping your card. I use an ATG or other dry adhesive. When I do need to use a wet glue, I use it very sparingly. You could also try running your folded card through your die-cutting machine (if you have one) before you add any embellishments to it.

My thoughts are the same as what riversong1963 suggested. The adhesive you use makes a difference. Liquid glue can warp the paper.

Another suggestion that I have is that it might be an issue with the weight of the card stock that you use. Heavier card stock doesn’t warp as easily.

I believe it makes a difference if your fold runs against or with the fibers of the cs. This would be easy to test.

I do want to add as an alternate opinion that I only use glue on my cards, even if I'm putting a full A2 panel on a card base. I just don't use tape runner at all any more. It's probably been a year or more since I completely stopped using it.

I have had no issues with warping or with my cards not lying flat. I use Bearly Arts, and do not over-glue. And I think I mentioned upthread that I use Hammermill 100lb and burnish it 3 times with a teflon bone folder (not a cheap plastic one). Most of my colored CS is also 100lb, so maybe the thickness of my CS is what helps the glue from warping the CS.

Thicker paper does warp less easily. The quality of the glue you're using also matters. I've had the best success with Aleene's tacky glue or Scotch quick dry. Aleene's is more traditional in consistency and has a bit of wiggle room before it sets up, and can warp if you blob it on. The Scotch version does not mess around, despite being a much thinner glue. Once it's down, it's down. For any glue, the less you use the better the results tend to be.

One of my pet peeves is watching crafty folk gluing up their projects and they're just *slopping* the glue on, like big fat daubs of it in only a few places. You want a thin layer of glue everywhere, it's not a burger condiment!