  We present a lumped-element Josephson parametric amplifier (JPA) utilizing a
straightforward fabrication process involving a single electron beam
lithography step followed by double-angle evaporation of aluminum and in-situ
oxidation. The Josephson junctions forming the SQUID are fabricated using
bridgeless shadow evaporation technique, which enables reliable fabrication of
relatively large ($\sim9~\mathrm{\mu m^2}$) junctions. Our strongly coupled
flux-pumped JPA achieves 20~dB gain with 95~MHz bandwidth around 5~GHz, while
the center frequency is tunable by more than 1~GHz, with the additional
possibility for rapid tuning by varying the pump frequency alone. Analytical
calculations based on the input-output theory reproduce our measurement results
closely.
