Just asking.. I keep seeing that the donation should be in an unsealed envelope... Ihad aprovidertell melast week that I should never have it in an envelope.. better just loose bills.. so now I am confused.. is there a standard? or simply preference?

you put the donation in an unsealed white envelope and leave it in an obvious place or somewhere that they specify.  Read their requirements.

on her website. When id doubt, meaning no information given, just use an envelope and leave it in plain site.  

...Did this lady say on her site that she didn't want it in an envelope? I've never seen a lady that specified no envelope. I have seen some that don't care either way after the first visit.

Is to do what the provider asks.  Some like it in an envelope, some don't.

I'll remember that if I ever see you!

But I still gotta ask if you would prefer an envelope shoved up your ass or individual bills. I may bring all singles.

I had a provider specifically ask that envelope be sealed. Wondered why.

You can either leave it on the night stand or the bathroom vanity if outcall.. Etiquette wise it's just better than being handed the donation in my hand. You can always remove it from the envelope if she prefers that...

But, I really don't care lol. I have had guys count the shit out and toss in at me after we were done, but they were guys I knew and it was more like a "here ya go hooker" joke. I certainly never used such practices because I am naive enough to think they combat LE or the implication of being paid for sex...I just find it less "businesslike" when it's not discussed and concealed.

Just be careful how you roll the bills.  LR won't let you shove em in her ass if they are rolled the long way.

Sometimes a gal will have instructions on her web site...  it might be well to follow those directions so she has some indication that you WILL follow instructions...  however, I quit envelopes years ago.  I count the donation several times to be sure it is right.  I put a paper clip on the bills to keep them together so no fumbling at the location.  I carry the donation in my key pocket separate from my other items.  
On a first date, I generally do the common place on the dresser or table routine.  If we are more comfortable on a repeat date, I'll find it more comfortable to empty my pocket junk on a corner of her dresser next to my clothes.  The first thing down is the donation.  When I redress after, the donation is silently left behind.  It is a bit more GFE/BFE illusion this way.  I've never had a complaint.  I did have one young provider...  third date but a long time since we'd been together...  who swooped in conspicuously to collect the donation while we were dressing.    
I think it is better to be exposed bills...  the gal can easily check quickly while you are washing up.  An envelope might be filled with newsprint or funny money...

Crinkled bills are so tacky.  
If the bills are crisp and new, and HUNDREDS, sure, no envelope, but looking up and seeing a pile of wrinkled twenties is not cute.