Page is flickering while parsing HTML in react component using shadow root

I am parsing HTML string to react component.
when I reload the page then first time response came from server and page render perfectly.
Now client side rendering start working and page become blank(flicker) for 1 sec. then again page rerender.

my HTML string size is around 300kb.

How I can overcome this flickering page between SSR and CSR?

For creating HTML string to Component page I am using following NPM package

• react-shadow

• react-html-parser

• htmlparser2

  <root.div
    className='htmlTemplate'
    mode={elem ? 'open' : 'closed'}
  >
       <style>{globalCss}</style>
       <div ref={this.setRef} className={className} {...rest}>
         {ReactHtmlParser(templateParser(template, templateData), {
           decodeEntities: decodeTemplate,
           transform: this.transform
         })}
       </div>
     </root.div>
  

Server side I am using ReactDOM.renderToNodeStream