05AB1E, 18 15 bytes
Code:
„/\5×{4Å6×»6F=R Explanation:
„/\ # Push the string "/\" 5× # Repeat 5 times: "/\/\/\/\/\" { # Sort, resulting in: "/////\\\\\" 4Å6 # Create a list of 6's with length 4: [6, 6, 6, 6] × # Vectorized string multiplication » # Join by newlines 6F # Do the following six times.. = # Print with a newline without popping R # Reverse the string Uses the CP-1252 encoding. Try it online!