Firstly: Realize and act, you should start loving it(Salah) yourself, feel and show hasten in offering it. Your child only observes what you do in household things and all activities which happen at home. He/she only idealize Parents i.e. (Mom) and his father.
Secondly: Make sure that instead of preaching him to offer Salah, you should work on making him love Allah and His prophet PBUH, create urge in your child by spraying characters of Salaf Saleheen, to love living life by the ways of Islam. Describe good stories to him occasionally, give him some role models whom he should appreciate & follow as a person (Our Prophet or his Companions, etc.), don’t give him coloring books of superheroes such as Batman/ Spiderman to observe and reflect, give him/her some Islamic coloring books.
Thirdly: gather him with good friends, visit masjid on every Friday with your child and manage to hold few good practicing mothers and their kids at your home even if its once in a week and meet and greet with them, it is highly recommended that fathers should take their kids along to Mosque five times on daily basis, show your kid example by practice more than word of mouth.
Lastly: Unless your child is well aware of existence & power of Allah, His Book (the glorious Quran), His Prophet (PBUH) and firmly believe in Hereafter. You cannot make him love Salah or any other teachings of Islam. The best way of doing it is to create an environment by first implementing and practicing same values yourself and continuously coaching you kids by being a role model yourself and with best of AKHLAAQ. (Wallahu Allam)