I am very much interested in free flight glider especially HLG/CLG. I tried a few times but didn't get much success.
can anyone please direct me to some good resource or book to get some knowledge on the subject?

This thread may help:

http://www.rcindia.org/kites-trains-free-flight-and-all-others/1st-chuck/

Best wishes.

thanks for the help, here is my first HLG.
getting a flying time of 17seconds.

Nice work, Abhilash. Congrats. For a first timer your launch technique is good. Cannot properly see in video, but transition appears good.

As i see the video, try adding a little nose weight, start with a pin head of clay and work your way up each time till the stall goes away and at times you see the wing rock. your are almost there .

try and get this book :https://www.thriftbooks.com/w/flying-hand-launched-gliders_john-kaufmann/748522/?mkwid=sznCWiYH7%7cdc&pcrid=70112861832&pkw=&pmt=&plc=&pgrid=21323637792&ptaid=pla-339024991645&gclid=CjwKCAjwsIbpBRBNEiwAZF8-zzL0TG0EyhyxFsclSTYHIyaj-TV9Lz4zSnKaD2SmBMarBS_gD1dPvRoCNSAQAvD_BwE#isbn=0688201083&idiq=32147664

a very well written book takes you through wood selection, building, carving aerofoil and trimming plus you will soon need a DT.
good luck.

thanks for the suggestion.
Already bought the book.
I tried to follow the design of this book while making one.