The counter bore area under the liner flange generally does not use sealer.
The typical thing to do is put the liner in without the seals, clamp it down with a hard bar and bolts, the check liner projection with a liner projection gauge or depth mic. If the liner is low or the counterbore area is pitted, it should be machined and shimmed back to spec.
If this is a "patch job" you can use a little thin liquid sealer under the flange, but beware that this usually does not last the expected service life.
The lower seal area should be clean. If it is pitted , fill the pits with JB weld or Devcon epoxy and hand sand them. When installing the liners, be sure the o-ring(s) are not twisted. Use a quality rubber lubricant (that tire installers use) or a mild liquid soap. I use a special tool to put them in, but a block of wood, an eyebolt in a head bolt hole and a prybar work fine. You just want a smooth steady push when installing.
"Nil Satis Nisi Optimum"