Yes, you can! To get your appointment you need a DS-160, and the DS-160 includes a question (that you can leave blank re: LCA). So you can fill the DS-160 in, leave it blank, book an appointment with your confirmed DS-160 number. Then when your LCA gets approved, file a new DS-160, now including your approved LCA number, and then contact the embassy you’re going to and ask to update your DS-160 (because “you needed to update the LCA details”). They should be completely fine with it and away you go. All embassy locations are unique, so it's important you check with the location you are applying to.