I have just told my children whaat I want, then it is up to them. You could write it down and give to the person who will be arranging your funeral, or you could talk to a local undertaker and agree everything upfront.
My aunt did this, liaised with the priest at her church, the undertaker and so that one phone call to the undertaker was all her husband would have to do.
It was more than just a prepayment plan. The priest knew what music was reuired and who would give the eulogy(me) and who to contact about any last minute arrangements. and she paid up front for everything, because she knew she would die before her husband, she was 10 years his senior and she had severe heart problems and she knew that because of his mental health problems, once she went her OH would be incapable of dealing with everything that followed.
Everything went without a hitch, as she had planned, when the day arrived.