Resin is a *massive* PITA factor for assembly. You basically need to pot the assembled PCB in the resin without getting any on the pins (or back side and edges if you are building a module for SMD mounting), hold the display face plastic in position against the PCB until it cures, and get a good finish on the segment faces. This will probably require tape to retain the resin, that is peeled off the display face after the resin has cured followed by polishing it. Many clear Epoxies would be suitable, probably with some white or coloured pigment added to obtain the desired degree of translucency
Another option would be graphic OLED displays. 30mm x 11.5mm displays are readily available and each could show three 10mm high digits with similar spacing to discrete 10mm 7 segment LED displays, or four digits if you use tighter spacing and narrower digits. If you need to emulate a multiplexed 7 segment LED, you'll also need a MCU that can read the segment and digit lines fast enough to keep up with the multiplexing and send appropriate graphics to the OLED whenever a segment changes.