Mark 11:22-24
22 So Jesus answered and said to them, "Have faith in God.
23 For assuredly, I say to you, whoever says to this mountain, 'Be removed and be cast into the sea,' and does not doubt in his heart, but believes that those things he says will be done, he will have whatever he says.
24 Therefore I say to you, whatever things you ask when you pray, believe that you receive them, and you will have them.
Who is the "them" to whom Jesus is speaking? The twelve disciples. Not you or me, or anyone else.
Does this verse stand alone in Scripture? Or are there other verses that qualify and clarify it? Well, yes there are other verses that do put limits and qualifications on this verse:
John 15:7
7 If you abide in Me, and My words abide in you, you will ask what you desire, and it shall be done for you.
James 4:3
3 You ask and do not receive, because you ask amiss, that you may spend it on your pleasures.
1 John 5:14-15
14 Now this is the confidence that we have in Him, that if we ask anything according to His will, He hears us.
15 And if we know that He hears us, whatever we ask, we know that we have the petitions that we have asked of Him.
You see, I hope, that Mark 11:24 does not stand alone as a verse on prayer. There are others also which we must take into consideration when we pray. It is not enough to believe and ask. One must ask according to God's will, and apart from selfish pleasures, and be abiding in Christ. I don't, then, see how Mark 11:24 is grounds for the Law of Attraction.
Selah.