I wish to create a GNU Radio program in C++ that doesn't need GRC or Python, is there a reference or template for this?
you can create flowgraph in c++ like gqrx and i think GNU Radio Manual and C++ API Reference documents will help you. This is gnuradio c++ document for top_block if you could not use it let me know to write a sample for you. These documents are for gnuradio version 3.7 and in gnuradio 3.8 there is c++ code generation and gnuradio blocks are porting to c++ and you can track them in this link.
i hope it helps.