I just found a little pack of 6 or so beef bones cut crosswise into about 1"/2cm thickness. I thought I'd try prepping them so as to use the marrow as a spread on crusty bread. But I'm new to this one. I don't know if or how they should be seasoned with salt and/or herbs prior to roasting. Do they dry-roast or do you use a water element somehow? And how long do they cook, and at what temperature? How do you know when marrow is "done"?