This was also very challenging but I made a template to help me out. I have put the link down below including where I think the treasure chest is.
2. The treasure map
Captain Blackheart buries his treasure but loses his treasure map! But all is not lost. His trusty crew remember different bits of the map.
"I remember drawing it with 5 squares each way", says the Captain.
"There was a row of three trees running due East from the square (1,1)", Peg Leg Pete says. "You put each one of them on a different square."
"Weren’t there four granite boulders going due South from (5,5)?" John asks. "I think you put one of them each in a square too."
"Ah!. Now I remember!" yells the Captain. "I buried the treasure half way between the first rock and the most western tree!"
Where is the treasure?