How do I write a code of ASCII text where I do not need to import like pyfiglet but do it manually and use whatever character of my choice in python

You can design the letters by hand with any character you wish (probably draw them on grid paper first), store them in a dictionary and write a function that composes each line of the output from the corresponding lines of the characters. It's quite some work to design a whole ASCII font by hand, but the function is quite simple:

def asciiart(letters,word=""):
    art = ""
    for line in range(letters["Size"]):
        for c in word:
            art+=letters[c].split('\n')[line]+" "
        art+="\n"
    return art
            
    

letters = {"Size":5,
           " ": "     \n     \n     \n     \n     ",
           "A": " ### \n#   #\n#####\n#   #\n#   #",
           "C": " ####\n#    \n#    \n#    \n ####"}

print(letters["A"],"\n")
print(letters["C"],"\n")
print(asciiart(letters,"AC CA AA"))

The output of this program would be:

 ### 
#   #
#####
#   #
#   # 

 ####
#    
#    
#    
 #### 

 ###   ####        ####  ###         ###   ###  
#   # #           #     #   #       #   # #   # 
##### #           #     #####       ##### ##### 
#   # #           #     #   #       #   # #   # 
#   #  ####        #### #   #       #   # #   #