Made a little white crackle box for my sister's baby last month and learned a few things the hard way, so sharing here in case it saves someone the grief. Fit your lid before you glaze, then glaze the lid and body separately and keep the seating area wiped clean. If glaze gets in there the lid will fuse or sit proud, and there's no fixing it after the firing.
For the crackle itself, thin coats beat thick ones every time. I brush on two light layers and let each dry fully. Thick glaze gives you big lazy cracks instead of that fine web people love. Pull it from the raku bucket while it's still hot and let the smoke do its thing, the carbon finds every crack line and that's what makes the pattern pop. One more thing, keep the box small-ish. Little forms cool fast and evenly, so the crazing stays tight and consistent across the whole surface. My first attempt was a chunky jar and the crackle went patchy where the walls held heat longer.