You are right that it is very difficult and it is quite rare at the top level. At lower levels even more so because players lack the skill and knowledge.
There was a highly instructive game played at the 2018 Isle of Man Masters between Sergey Karjakin and Sam Sevian which demonstrated the mate and some of the principles involved.
As you say the idea is for the side with the knights, let's say White, to blockade the pawn with one of the knights, drive the Black king into a corner and then deliver mate by using the other knight to come over and put the king into what would be a stalemate position were it not for the pawn with mate next move.
There are a number of principles for both the attack and the defense.
- The further up the board the pawn is the more difficult it is to mate because the fewer moves the blockading knight will have before the pawn queens and joins the fray. Once the pawn reaches the 5th rank the mate becomes problematic and on the 6th rank only possible with a Black blunder.
- The closer the pawn is in files to the mating corner the easier it is to mate because then the knight has to make fewer moves. This means the defending king should head for the corner furthest from the pawn.
- If the Black king can attack the blockading knight it can generally force the pawn forward and increase the chance of a draw so the idea for White is to drive the Black king either to the back rank or the side of the board.
- The key "driving" position occurs when the White king and knight are next to each other and the black king is a knight's move in front of the White king. Then the Black king is driven backwards/sideways.
- In general the White king should stay away from the pawn and blockading knight unless it can force the blockading knight to move. The problem being that approaching the pawn also brings the blockading knight into play to block off squares for the White king.
In this game the K+N+N vs K+P endgame starts on move 58
The pawn is finally blockaded on the 5th rank on move 61
The first "driving" position occurs on move 64 with the White king all the way back on the back rank with the White king needing to be driven both backwards and away from the blockading knight.
Further examples of the driving position occur on moves 67, 74, 80 and 84
The Black king is far enough in the corner for white to lift the blockade and use the other knight on move 89. Black doesn't immediately move the pawn.
You can see what would have happened if black had immediately moved the pawn in the variation from Black's move 89 and this is instructive because it shows the stalemate point. Without the pawn White's move 92. Ne7 would be stalemate.
[Title "Karjakin vs Sevian 2018 Isle of Man"]
[fen ""]
[Startply "116"]
1. e4 e5 2. Nf3 Nc6 3. Bb5 a6 4. Ba4 Nf6 5. O-O Be7 6. Re1 b5 7. Bb3 O-O 8. a4 b4 9. a5 d6 10. d3 Be6 11. Nbd2 Qc8 12. h3 Rb8 13. Nc4 h6 14. Be3 Rd8 15. Qe2 Bf8 16. Nfd2 g6 17. Ba4 Qb7 18. Qf3 Nh7 19. Qg3 Bg7 20. f4 exf4 21. Bxf4 Nf6 22. Be3 Nd7 23. Qf2 Nc5 24. Bxc6 Qxc6 25. Bd4 Bxd4 26. Qxd4 b3 27. c3 Nd7 28. Qe3 d5 29. exd5 Bxd5 30. Qxh6 Re8 31. Ne3 Ne5 32. c4 Bxg2 33. Nxg2 Nxd3 34. Re3 Qc5 35. Kh1 Nf2+ 36. Kh2 Qd6+ 37. Kg1 Rxe3 38. Qxe3 Nxh3+ 39. Kh1 Kg7 40. Re1 Rh8 41. Qe5+ Qxe5 42. Rxe5 Ng5+ 43. Kg1 Rd8 44. Rd5 Rxd5 45. cxd5 Kf6 46. Nxb3 Ne4 47. Ne3 Ke5 48. Kg2 f5 49. Nc1 f4 50. Nc2 Kxd5 51. Nb4+ Kc4 52. Nxa6 Kb5 53. Nxc7+ Kxa5 54. Nd3 Nd2 55. Ne6 Kb5 56. Nexf4 Nc4 57. Ne6 Nxb2 58. Nxb2 g5 59. Nd4+ Kc5 60. Nf5 g4 61. Ng3 Kd4 62. Kf2 Kc3 63. Nd1+ Kd3 64. Ke1 Kc4 65. Kd2 Kd4 66. Nc3 Kc4 67. Nce2 Kd5 68. Kc3 Kc5 69. Nf4 Kc6 70. Kc4 Kd6 71. Nd3 Kc6 72. Ne5+ Kd6 73. Kd4 Ke6 74. Nc4 Kf6 75. Ne3 Ke6 76. Nef5 Kd7 77. Kd5 Kc7 78. Nd4 Kd7 79. Ne6 Ke7 80. Nc5 Kf7 81. Kd6 Kf6 82. Nce4+ Kf7 83. Kd7 Kf8 84. Nd6 Kg7 85. Ke6 Kg6 86. Nde4 Kg7 87. Ke7 Kg8 88. Kf6 Kh7 89. Nf5 Kg8 (89...g3 90. Kf7 g2 91. Ng5+ Kh8 92. Ne7 g1=Q 93. Ng6#) 90. Ke7 g3 91. Nf6+ Kh8 92. Kf8 1-0
