# [Ruby](https://www.ruby-lang.org/en/), <strike>80</strike> 76 bytes

-4 bytes thanks to manatwork

    puts"\\";$*[i=0].chars.each_cons 2{|b,c|puts" "*(b==c ?b==?/?i-=1:i+=1:i)+c}

[Try it online!](https://tio.run/##KypNqvz/v6C0pFgpJkbJWkUrOtPWIFYvOSOxqFgvNTE5Iz45P69Ywai6JkknuQasTkFJSyPJ1jZZwR5I2uvbZ@raGlplaoMITe3k2v///8fExOjrx@jHxAAA "Ruby – Try It Online")

Explanation:

    puts "\\"			# Output the first backslash
    $*[i=0].			# Get the first argument and set i to 0
    chars.			    # Go through every individual character,
    each_cons 2 { |b,c|	# In pairs to compare easily
    					#
    	puts " " *		# Decide how many padding spaces to use based on the value
    					# of i. The expression inside the parenthesis will return
    					# i but before that, it will increment/decrement i based
    					# on what the previous character was.
    						#
    	( b==c ?			# if b == c
    		b==?/ ?			# 	if b == "/" (Going to the left)
    			i-=1		#   	return decremented i
    			:			# 	else        (Going to the right)
    			i+=1		# 		return incremented i
    		: 				# else
    		i) +			# 	return i
    					#
    				c	# Finally, write the second of the characters that we're
    }					# iterating through.