Either from PyPI:

python3 -m pip install makemake90

Or from GitHub:

python3 -m pip install git+https://github.com/janberges/makemake90

Generate Makefile for all .f90 files in the current directory and its subdirectories, optionally indicating special directories of your project:

makemake90 src=src obj=build mod=build bin=bin

Customize Makefile preamble (before the line with generated by makemake):

$EDITOR Makefile

Build your project:

make FC=gfortran FFLAGS=-O3

Update Makefile after further work on project:

makemake90