A quick guide to croissant lamination for beginners

The matching temperatures thing took me three batches to figure out too, and what finally made it click for me was buying a cheap probe thermometer and actually checking instead of guessing. I aim for the dough and butter both around 60F before I start rolling, and my kitchen in summer runs warm enugh that I now roll on a sheet pan I keep in the freezer for a couple minutes first. Where I differ from you slightly is the folding. I do two letter folds and one book fold instead of three letter folds, and I find the book fold gives me more layers without adding another full chill cycle. Takes a bit of practice to get the corners even, but once it clicks it clicks. I also started marking the baking paper with a pen so I know how big the rectangle should be at each stage, which stopped me from drifting into uneven thickness without noticing.

The thing that got me on my early attempts was proofing. I'd laminate fine and then let them rise somewhere too warm, and the butter whould soften and melt out the bottom onto the tray. Now I proof them in my garage overnight when it's cool, or in the oven with just the light on and the door cracked. Slower rise, way better oven spring, and no puddles of butter to clean off the pan in the morning.

Gotta push back on the oven with the light on thing. That trick is way oven-dependent, mine gets warm enough with just the light that the butter went soft on the bottom of the dough and I had the same puddle problem you were escaping. An oven is insulated, so a little bulb holds heat in there more than people expect. A cool room and patience gets you the same slow rise without gambling on wheather your particular oven runs hot. If you want to use the oven method, at least leave the door propped properly and check the dough feels cool to the touch before you walk away.

Lurker here, first post, so bear with me. I've only done rough puff for sausage rolls and always wondered why my croissant attempts years ago flopped. Reading this I'm pretty sure I was laminating way too cold, like rock hard butter cold, and tearing the dough apart. Is it worth trying croissants with a half batch first or does the smaller dough make it harder to roll evenly? Mine always ended up wonky.

Update: the thermometer suggestion from that first reply sorted me out. Turns out my 'equalized' dough and butter were actualy a fair bit apart, so now I actually check instead of guessing. Even my second fold is coming out clean. Still struggling with the last roll though, the dough goes slack and sticky about halfway across the board. Do you folks chill again right before the final fold, or just power through?