Making a will in legal way

If the property is self earned by your father and the same are on his name then he has all rights over them, he can will them, gift them he can use them as per his wish noone can interfere , if he wants to give his property during his lifetime then registered gift deed is the very best and safe option, if he wants to give after his demise then registered will deed is the best option, i suggest you tell your father to go for gift deed because during his lifetime nobody will object if anyone objects he can answer them but in will deed it can be challenge in the court of probate and then takes years to decide, because your father will not there to answer .

My sisters have children and are married for more than 14 years ago.

My father's property is self acquired and not ancestral. But due to disputes my sisters no longer talk to my parents or me.

then he can gift it to you or he can will it on you.your sisters cant lay any claim as it is her self aquired property

Your question is about executing a Will by your father bequeathing his property.  You have also confirmed that the property was his self acquired property.  In the given situation, he can very well bequeath his entire property favoring you or anyone of his choice by executing a Will accordingly.  Your sisters cannot claim a share in it once the Will is accepted and enforced.