  X-ray binaries in outburst typically show two canonical X-ray spectral
states, i.e. hard and soft states, in which the physical properties of the
accretion flow and of the jet are known to change. Recently, the JED-SAD
paradigm has been proposed for black hole X-ray binaries, aimed to address the
accretion-ejection interplay in these systems. According to this model, the
accretion flow is composed by an outer standard Shakura-Sunyaev disk (SAD) and
an inner hot Jet Emitting Disk (JED). The JED produces both the hard X-ray
emission, effectively playing the role of the hot corona, and the radio jets.
In this paper, we use the JED-SAD model to describe the evolution of the
accretion flow in the black hole transient MAXI J1820+070 during its hard and
hard-intermediate states. Contrarily to the previous applications of this
model, the Compton reflection component has been taken into account. We use
eight broadband X-rays spectra, including NuSTAR, NICER and Swift data,
providing a total spectral coverage of 0.8-190 keV. The data were directly
fitted with the JED-SAD model. Our results suggest that the optically thick
disk (i.e. the SAD) does not extend down to the ISCO in any of the considered
epochs. In particular, as the system evolves towards the hard/intermediate
state, we find that the inner radius decreases from $\sim$60 R$_{\rm G}$ in the
first observation down to $\sim$30 R$_{\rm G}$ in the last one. This trend is
accompanied by an increase of the mass-accretion rate. In all hard-intermediate
state observations, two reflection components, characterized by different
values of ionization, are required to adequately explain the data. These
components likely originate from different regions of the SAD. We show that a
flared outer disk could, in principle, explain the double reflection component.
